We will need small and independent commercial providers for the Fediverse.
Wikipedia is also actively used by practically anyone that has a connection to the internet, too. Something like Lemmy has way higher costs per user (both financial and computational), and a significantly smaller user base.
Except that the hosting costs of Wikipedia are neligible. Have a look here: https://en.wikipedia.org/wiki/User:Guy_Macon/Wikipedia_has_Cancer