there's no such thing as an ethically sourced residential proxy.
Even these soft reasons to use VPNs and residential proxies are like an alibi for bad actors, is IP 25.14.xx.xx creating a fake account on twitter to spread malware or is he downloading a show that wasn't available before? I guess we'll never know such are the limits of privacy I guess.
The internet in a growing number of countries is censored, but different content categories are censored in each jurisdiction. Many sites and services also block known VPNs (i.e. non-residential IPs), so that doesn't work as a bypass in all cases.
I have trusted friends in other countries, so by mutual agreement we could set up wireguard links for each other to use (subject to agreed terms). It just needs some way to intelligently route traffic depending on which jurisdictions will allow which requests (i.e. "which is the lowest-latency link that will allow this request").
That thing already exist and is called Tor Snowflake.
There is, just like you giving your attention and cpu to watch free ad supported content on the internet. It's the same in apps that give users access for free in return for bandwidth, or free VPNs that allow you to share bandwidth. There's also ISP "residential" proxies where ISPs re-sell some of their address space to proxy providers.
In practice, the vast majority of residential proxy usage would be for other (non-ethical) purposes.