Because it is illegal. The fact we can use DVRs in our homes for personal use is lucky - Universal and Walt Disney sued Sony over their Betamax VCR in the 70s, claiming that it was a device intended for copyright infringement. Technically, recording a program and watching it later infringes on the copyright as it is a "rebroadcast". Luckily the Supreme Court held (in a very narrow 5-4 victory that almost didn't happen) that it was 'fair use' under copyright law, which allowed for in-home recording.
That fair-use exemption is not true for public viewing like in a bar or restaurant. It is actually a violation of copyright to show copyrighted material in public like that, the only way in which it is legal is if it is specifically allowed by law (which it is for OTA TV and radio only) or by contract (like when you pay commercial public viewing rates for Directv) They would have to specifically allow use of a DVR in their commercial contract with Directv. They do not, thus if you brought a DVR from home to use you could be sued by ESPN (or whoever owned what you recorded and played back later) for copyright infringement. Which is a fine of up to $150,000 per incident.
Anything that doesn't specifically allow for 'public performance' isn't legal. So no Netflix, HBO Go, Apple Music, Spotify, Directv Now, Sling TV, ESPN3, etc. etc.
