Doing DVDs-by-post makes sense (makes cents?) because their mailing cost is negligible and library operations can likely be fully-automated - and low media-costs mean damaged, lost, and unreturned media won’t materially affect the business.
VHS-by-post, on the other hand, has issues:
* Large bulky media will cost far more to mail because it can’t be handled by existing postal equipment for letters/envelopes.
* Tape signal damage caused by EM fields - I don’t expect 1970s/1980s post office equipment to have much EM shielding.
* VHS picture quality is awful: people subscribed to HBO instead.
* Handling: DVD libraries are automated thanks to barcodes and robots - both of those things weren’t really ready to build a VHS-by-mail library. Not to mention needing to rewind tapes.
While web streaming becoming popular (and the selection available for streaming becoming much wider) definitely dealt a killing blow to Blockbuster, Netflix was already successful with their mail-in rental service, and had made a name for themselves with it.
Like this? AKA, the "original" Netflix.