This is clearly not true, or the CAIDA anti-spoofer project wouldn't exist.

https://spoofer.caida.org/summary.php

Just because SOME ASNs don't have it in place doesn't mean it's not uncommon. In the link provided, 80% of all tracked network blocks for ipv4 are blocking spoofing. Though they only track 1000 ipv4 /24 blocks and their data is highly biased towards having spoofable ranges, considering their end goal is identifying spoofable networks!