This is from a US small non-profit, and small for-profit operating with way less than $1M in funding, and not necessarily intending to deal with people in the EU context: Not every company has money to pay for the hours to ensure they are GDPR compliant, so they opt out of serving EU clients altogether. It's not always a problem forever, but it's definitely a blocker sometimes.
How is it any different than an EU company complying with Russian/US/whatever laws?
International laws have always been crazy expensive, if anything, being able to (mostly) target quite a big market by only making it EU-aware is more of a plus, than a negative.
That’s the thing: when I come onto a project they might not even know, nor have the hours to allocate to figure it out, and I ain’t working for free to figure it out.