The internet is pretty unreliable as it goes, and the internet in your locality is probably only one network (e.g. Comcast's) - what are you gaining by running critical systems over Comcast internet access, instead of Comcast leased line? Saving a few hundred bucks a month, yes, but that's because you're getting less reliability than you actually need.

Also lower MTTR and more robust SLAs in many cases. Business services will usually result in service credits being issued if the SLO is breached. Residential... not so much.