What if not GDPR would make an american B2C startup intentionally block visitors from Europe? Their investors most likely fly in and out of Europe all the time and want to show their portfolio company to their buddies. The startup's growth case is international expansion.
AirAnswers is not a startup as I originally thought, it seems to be a ten year old company with mature product and a set of patents they mention in marketing materials. If they block EU customers it's definitely a conscious choice.
Why do you say that’s the most likely reason? You can’t imagine other plausible reasons?