1. It depends on what part of the world you are in, but many homes have cooling needs for at least part of the year. The needs to remove excess heat would go up if you are adding more heat -- and it is less efficient to do this at the scale of an individual home than it is at DC scale.
2. Power requirements: While many homelabs have UPS systems -- they lack often lack backup generators, redundant A+B power infrastructure, and don't have the required power density for higher powered servers.
3. Connectivity requirements: most homes don't have access to the connectivity that data centers do.
4. Security requirements: homes simply can't meet the security requirements of most data protection regulations -- things like barriers, access control systems, surveillance, fire protection -- are anywhere from intrusive to completely impossible in a home.
5. Access requirements: homes aren't conducive to a technician responding to an outage at 3am
And those are just the big ones.