Because renewable depends on the weather, while nuclear doesn't.

A mix of renewable is absolutely a good thing to do, but still, having a constant source of energy mixed with that ensure stability.

The storage problem is the limiting factor. Batteries are wildly too expensive, pumped storage takes a huge amount of space and isn’t feasible in most places due to geography, and hydrogen is not nearly there yet technologically.

If we switched entirely to wind and solar we would need to accept total shutdowns when we had a bad run of weather.

last time I checked the renewables being installed didn't even offset the new energy demands being created, let alone making a dent in starting to decarbonize existing demand.

and the main reason is, that we need to tackle climate change from as many angles as possible and not eliminate a fine energy source just because something else is cheaper.

I mean for now renewables are cheaper, do you think we have enough raw materials to cover all of earths energy needs?

what happens when the raw materials will start to run dry but we still need to cover a bunch of energy needs, is that when we dust off the good ol Nuclear plants?

not to mention Nuclear plants provide a stable base load, no need for smart electronic devices that use power when it's most abundant etc. it's just power, that runs, constantly.

Adding to what others have said here, nuclear is great for base load consumption. Use the renewables to supplement during peak hours where load variability is the greatest.

Sure, you could connect renewables to batteries / accumulators for times when they are not available (i.e. no wind, no sun) but this doesn't give a very good consistent base load. A nuclear plant that is 1 MWe will always give 1MWe if it is up all the time. I'm not saying here that batteries aren't a good option, just that they aren't the optimal solution.

Another thing to consider is resistive transmission losses. Connecting long cables from, say offshore wind farms or areas of high wind density, to electrical substations long distances away makes delivering the electricity more inefficient. Granted, having it is better than not (nobody likes brownouts). But engineers try to take all of these into consideration when working on the regional power grid.

I think the issue is batteries, which are expensive and require rare earth metals which often have environmentally costly acquisition methods. Perhaps an optimal solution would be a baseline of nuclear power, and then enough renewables to meet peaks in demand. That way we have plenty of stable energy while minimizing nuclear risks.