Wrong
look at the competition to nostr that is actually booming.
people love free
making social about money will deter people
zaps was good to pay people for stuff but making relays cost money is anti-pattern
Discussion
It's because Nostr is new. Not many people know or have heard about Nostr.
The second problem is that Nostr isn't a website or app. You have to do this strange thing of using a nsec and people are used to using passwords and centralized websites.
It will take time but Nostr will win.
No one is making relays pay. The free relays are beating the paid relays. It's up to the relays administrator.