Because most of the numbers coming out of the nuclear sector for this are too good to be true. To put it mildly. It's tempting to use more harsh language here. Like "fabricated nonsense" or "a scam". And some people do.
Probably the biggest challenge for nuclear proponents aside from demonstrably high cost, overruns, wildly optimistic timelines, etc. for past projects is the credibility of their predictions about cost for future ones. The lower those predictions, the smaller the chance that those are anything more than wishful thinking mixed with a lot of hopium and based on very flawed assumptions.
When cost overruns in nuclear projects are routinely measured in hundreds of percents, something is very wrong. It would be nice to get that down to two digit percentages. That would still be terrible but a lot better than the industry norms for this. Especially compared to renewable projects.
This credibility challenge is a large part of the reluctance of investors to fund new efforts in this space. Most of the projects that actually still happen feature governments and tax payers taking most of the risk. Which makes it more likely that the huge budget gaps get funded rather than resulting in investors cutting their losses and bailing.
If you want numbers, look at numbers of GW coming online for nuclear, wind, solar, and energy storage projects. There's a stark difference there. Renewables are outpacing nuclear at such a pace that you could legitimately wonder why to bother with such projects at all.
Indeed, especially as renewable will more and more eat into nuclear 'baseload', lowering its load factor and therefore raising its total production cost. https://www.youtube.com/watch?v=udJJ7n_Ryjg
Cheap and expensive in dollar terms is meaningless. Dollars are numbers in computers. Joules and watts are real.
What I can agree with we need good enough EROI energy and then adjust the policies regarding fusion, nuclear and fossil joules, watts and their related numbers in computers.