They get the attention and business of people like me who actively avoid vendor lock-in. I'm very open to (and often end up becoming a paid customer) products that have open options, and I also typically bring my org along with me. Most recently I did this with Tailscale. (Note: If not for the Headscale project, I would never have become a Tailscale customer so their openness is gained them at least one ARR of about $2k that they otherwise would not have gotten)

I also tend to self-host my personal stuff but pay for hosted for the business, knowing that if the product changed in unsavory ways (pricing, closed-nature, etc) the business could self-host and escape a hostage situation. It's far from perfect as usually there's a bunch of data in their DB that you can't easily export, but with proprietary/closed solutions that's nearly guaranteed to be the case.