> Presumably a nicer website could lead to more customers.

It depends what "nicer" means. Paying a web designer/developer to create a bespoke website doesn't guarantee that said website will have a better UI/UX and, most importantly, "convert" at a higher rate. Not every web designer/developer understands IA, content, performance optimization, etc.

The popular AI tools produce websites that are clearly AI-produced if you know the patterns, but that doesn't mean they can't be usable and quite effective at converting. And if you have a bit of skill with prompting, AI can be really good at working through performance bottlenecks, etc.