Because a company being unable to comply with GDPR is a red flag for how they treat user data. GDPR is written in such a way that you as a company are given freedom to use data if its for business reasons. But you need you need to keep track of it.
Enhanced data protections are a good reason to (by default) be a European.
Same with the cookiewall, by the way: if you need a cookie wall, that means you do more than aggregated statistics such as building profiles of individuals. Even if you have accounts, you don't need a cookie wall for a login system. Only if you do tracking. People see it as "govt doesn't understand tech again" but I think in reality, it's the people that completely missed the point here.
I think the point is that this would be a good reason to go elsewhere. However, if you have already signed up, it is a silly way to lock yourself out of something you have signed up for.
Which is to reveal the point of the VPN idea. Instead of having to do a lot of extra research on all companies you deal with to know who can comply with the style of rules that GDPR requires, being VPN'd might force them to reveal themselves to you.
At least, that is my guess on what each of those posts was getting at.
I think the GP is assuming that there will be services that don’t close to the EU; nor become 100% GDPR compliant for every user; but rather become GDPR-compliant for EU users while continuing to sell the data of non-EU users.
Enhanced data protections are a good reason to (by default) be a European.