Noticed that. It used to be easy to bypass, because old.reddit.com allowed me to go there with a VPN, but they recently patched it. I found that changing the user agent to make it look like you're on Chrome and Windows, alongside with US/Canada VPNs tend to get around this, but it isn't very reliable.
Stealth used to work for a while, but not anymore either.
They are doing it to stop scrappers scrapers and punishing people who use a VPN is just a bonus to them.