That's not them doing something wrong though. There's nothing wrong in hosting a server at home. The problem is clearly the black/grey lists if they black/grey list residential IPs just because.
Now most of them do not actually enforce it unless you become a problem, but most of them do put active measures on the network to stop SMTP Servers
For example here is a Exerpt from Comcast AUP prohibiting email and web hosting [1]
>>>use or run dedicated, stand-alone equipment or servers from the Premises that provide network content or any other services to anyone outside of your Premises local area network (“Premises LAN”), also commonly referred to as public services or servers. Examples of prohibited equipment and servers include, but are not limited to, email, web hosting, file sharing, and proxy services and servers;
[1] https://www.xfinity.com/corporate/customers/policies/highspe...
Why? Google Fiber is Available to less than 1% of US Households. Comcast is the largest Residential ISP last I looked in about 60-70% of US Markets...
ATT has the same policy, and I believe most of the other Cable Providers do as well. My guess would be over 90% of Residential Internet Plans today have a policy inline with Comcast not Google Fiber
Pointing to an outlier to the norm does not mean i need to update my worldview at all.
I looked for market share info on Google Fiber but was unable to find it. Mind sharing your source?