Using BGP would be overkill for most. Many small commercial customers
to not want the complexity of BGP
This one keeps coming up.
Leaf-node BGP config is utterly trivial, and is much easier for the SP to configure the necessary safety devices on their side to stop you from shooting yourself in the foot and blowing up your networks - or worse, *their* network. Plus, if / when in the future you need to do something clever, you've already got the routing protocol with all the advanced knobs in place, ready for you to tweak as needed.
The Enterprise guys really need to get out of the blanket "BGP is scary" mindset - running BGP for an SP with multitudes of customers, peers, transits, aggregation, filters etc and getting it right needs expertise and experience. Announcing a /24 LAN and receiving a default on a single link, not so much.
or want to spend money on extra
resources (routers that actually support it)
This has a bit more weight to it, if you're at the really low end (certainly the consumer end). But a BGP-capable Cisco 800-series is, what, £300?