Secondly, it makes passive surveillance and data gathering much harder. You can still track which sites a user connects to, but you can't see which pages they access or the contents of those pages. You can still actively intercept those connections via MitM but that requires users to manually install an MitM certificate on their system so they should be aware when it's occurring.
Thirdly, it makes it harder to intentionally block or break HTTPS altogether at the network level to force users to fall back to unencrypted HTTP. (TLS downgrade attacks are different from and much more difficult than, for example, just blocking all traffic on port 443.) If there's no unencrypted fallback, then users will complain loudly when they can't access sites.
If your main concern is old computers the solution is to use a proxy that strips the encryption.
[1] https://www.bankinfosecurity.com/github-hit-by-its-largest-d...