They were uncommon because they were uncommon. That’s why there was a business installing them. If they were common nobody would have bought them from you.

Wifi networks are very common today, and yet there are heaps of businesses installing them (and they normally have to install Ethernet at the same time, to connect the access points to the broadband router/modem). The same is true of air conditioners, solar panels, household batteries, rainwater tanks, surveillance cameras, building alarms, fire alarms, fire suppression systems, elevators

Your suggestion that the existence of businesses installing something is evidence the thing is uncommon, is illogical