I'm not questioning your experience but this is very strange to me.
I've worked with contractors based in Brazil, Turkey, and other countries likely categorized as "developing" and the payment process doesn't look any different than when I work with international contractors in places like Germany.
Many of them use Wise (formerly TransferWise) and looking at the pricing for Nigeria it looks completely reasonable - sending money has a 0.41% fee and receiving it is free. This fee includes reasonable things like a website non-crypto enthusiasts can actually use, customer support, fraud protections, etc. For countries with unstable currencies, massive inflation, etc Wise allows you to hold it in over 50 fiat currencies (including USD).
Given that I've had an interest in crypto for many years at this point I've seen online descriptions like yours so I've asked the contractors I've worked with "Why not crypto?". They all tell the same story - that services like Wise are perfectly usable and with extremely reasonable pricing all things considered. Wise even provides the sending of invoices that I (as the client) receive via e-mail and can pay in a few clicks. The most important thing to people is actually getting paid and it's a well known fact that reducing friction around payments is the best thing you can do (I've been a contractor as well).
Note this is technical/development contract work. I can't imagine people in non-technical fields getting an invoice asking for payment in crypto stablecoin and them spending the time, energy, and resources to wander through that maze to pay a contractor, service, etc instead of running their business. Frankly I'd use a different contractor and I'm very crypto literate.