New single-family house in southern Germany

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In my opinion, this no longer fits in today’s time.
Party basements had their heyday in the 70s-80s (!?) and nowadays I don’t know anyone who still uses theirs.
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My father converted a basement room into a party basement decades ago and called it "Zum fliegenden Ei". I do not know the origin of the name, but I can say that the party basement has experienced a lot and was well used over many years. Even today it is still regularly used—in a somewhat modernized form—by my nephew (early 20s) and his "gang". Friends of ours also have a well-equipped party room (not in the basement), which was used very often and—after Corona—has been used more frequently again. The multitude of sometimes spontaneous events is not something you want—at least I don’t—in your living space, even though I certainly don’t have to "hide" my living space :)

The multitude of - partly spontaneous events - one does not want to have - at least not me - in the living room,

Come on. The best parties always end up staying in the kitchen :p

Yes ... we rarely managed to have visitors even in the dining area - except for more formal occasions. Visitors have never sat on our couch. That’s why we would probably place greater value on the kitchen in a new building.

Come on. The best parties always stick around in the kitchen :p

Not with our friends who have a party room ... :D That one is legendary!

let me complain too before I fix my little crown again!

But of course. That’s allowed sometimes ;). I also understand you when you invest your time and then there is no or not the expected feedback. But I am also a hard case of being resistant to advice/negative learning curve and think that I can therefore empathize with the OP.

... True, not quite as much for 20 years now, but in my life, I have seen different such transient "standards" come and go. What is sometimes gladly considered a "standard" today will be outdated in 20 years, and we don't yet know what it will look like.

Maybe the standard will develop back into a basement in the next two or three decades. That would of course massively negatively affect the resale value of houses without basements. After all, Corona shows us how important sensible storage (including toilet paper) can be in the event of a quarantine ... :D And who knows what else is coming? Who expected something like Corona with all its restrictions? What’s next? Maybe an alien invasion or a natural disaster? People with basements and corresponding storage and shelter potential (see among others "War of the Worlds" and "10 Cloverfield Lane") will triumph! That would of course massively negatively affect the resale value of houses without basements. We don’t have a "real" basement either. But since the house is on a slope, more like a walk-out basement – so rooms with "normal" windows. In the walk-out basement is the laundry room – nowadays called a utility room, in short utility room – the heating, the "man cave," and two small storage rooms as well as access to the garages. So the walk-out basement is used just like the upper floors. I find the fundamentally different opinions on the topic of party rooms and bathtubs fascinating :D I have stated several times that we consciously decided against a bathtub to install a larger shower. We never (!) missed having a bathtub. There are no small children living in the household and none will come anymore. Grandchildren maybe ... Will a bathtub be longed for in old age? No idea. Hopefully at least in the later nursing home there will be nice big bathtubs where I will be lovingly bathed ... That a bathtub now impairs the resale value, I don’t consider very likely, although it also depends on the market situation. The real estate market is so tense that in some areas you can be glad to find a house at all. Would such a house be rejected because of a missing bathtub? Possible ... but how likely? If we had the space in the bathroom, we certainly would also have a bathtub for the sake of "completeness" – especially in a new build. However, I estimate the additional financial expense as not insignificant. Maybe a bathtub will also be omitted in the future for cost reasons, as houses become more and more expensive. Not everyone installs a fireplace anymore either. In addition, water – also here with us – is becoming scarcer. Already today, there are areas in Germany with significant water shortages. Here I can again name acquaintances of ours whose girlfriend showers because in their own area – no joke – water is scarce! In short: if you want a bathtub, just install one :) If you want a basement, build one and if you want a party room, build one :)

With a cold, straight into the bathtub, there is nothing better. Except ...... , without a cold, straight into the bathtub.;)

Or warm beer with honey through the nose ... works wonders!