There are no good reasons. Filtering implies opex, capex and man power. Also some customers are anti-filtering, basically accept everything or we wold leave to

There are no good reasons. Filtering implies opex, capex and man power. Also some customers are anti-filtering, basically accept everything or we wold leave to another uplink who won't filter us. I would say ~30% of organisations do not maintain their IRR data properly, notably this https://www.apnic.net/get-ip/faqs/route-management/ https://www.apnic.net/get-ip/faqs/route-management/ and https://www.apnic.net/manage-ip/using-whois/guide/as-set/ https://www.apnic.net/manage-ip/using-whois/guide/as-set/ (same fotr ARIN, RIPE, AfriNIC)