Absolutely. But this begs the question that businesses want to also sign up to maintain whatever product they've built, on top of their core business.
"Service" is the word that people seem to be forgetting in SaaS. If you roll you own, all you have is software.
But yes, this brings us back to the point that simply building the tool is only a small part of the process...and it has often been one of the most expensive parts of the process.