How do I destroy this weed on the balcony?!

@Danni:
"But basically the question is, why did the slabs have to be laid with gaps?"
Answer:
The laying of terrace slabs with joints must simply be done because every object, gas or liquid expands when heat is applied.
The surface temperature of an outdoor covering can reach up to +60°C depending on the color. If the slabs were laid "butted tightly," compressive stresses would occur in the covering plane that need to be relieved somewhere. Ideally, they are relieved in the joints; otherwise, bulging would occur if the slabs press hard against each other at the edges.
Regards: KlaRa

Thank you KlaRa, maybe I formulated the question wrongly, so why are they not allowed to be grouted. They lie on a kind of granulate and there is nothing in the joints. To prevent dirt from being swept in there, I vacuum the balcony. That’s also crazy. But still, I now see 1000 little green plants in the joints, one next to the other. Even if I were able to pull them all out with tweezers, which would be a Sisyphean task, new seeds would always settle and germinate there. Which, by the way, has already happened: there are tripping spots because some tiles, it’s only a few millimeters, are no longer level. Previously we had grouted granite tiles. That was great. But the building management or their architect didn’t want that anymore. Now there are tiles, I think they are called porcelain stoneware. The way they lie, can’t they also move?

Best regards, Daggi