For example if you are running a SaaS website which only caters to customers in the US what is the advantage of letting IPs from China or Russia access your service? Those IPs are not going to utilize your service because you don’t offer services outside of the US; since the IPs cannot be used for legitimate actions they can therefore only be used for illegitimate actions and should be blocked.
That's literally being hostile to your customers where they may be under more pressure than normal to resolve whatever they're trying to achieve.
I’m honestly a bit surprised to see so many people attempting to counter the idea that some businesses don’t need to be accessible from every region in the world.
just imagine for a moment people may want to send gifts for their loved ones.
But even if you don't mind doing so... Our company didn't have any outside-the-US employees - until we did. We hired one remote in Canada, and we hired some contractors in the Philippines and Portugal. So you're creating a situation where either you have to fix your ability to let people connect from outside the US right now (with all the security issues that may cause, which you also have to fix right now), or else you lose a customer each time something like that happens.