I mean there is some reason not to, at least until proper alternatives are set up. I work in the HV industry, and in my opinion we’ve rushed to close larger, relatively efficient coal plants and replace them with smaller, far less efficient diesel and gas generators that can be hidden behind tall fences in industrial estates. These pollute far more per MW than coal plants, but they’re out of sight, out of mind.
We definitely should be going hard into current renewable technology to fill out demand. That’s the fastest way to net zero in many regions. There is something to be said for big rotating generators though, ie large turbines, as these provide voltage and frequency stability - renewables are often inverter driven, even wind turbines, so these are always following the grid and can destabilise if voltage or frequency goes. Meanwhile, a large machine has inertia so it will want to keep spinning and maintain the same output when large loads switch in and out. This sort of thing can be provided by nuclear power. So if we build lots of renewables now to get clean, then build nuclear to fill out, that might be the best solution.