Would you mind sharing which other saas products you are so posting?
Well the bare minimum that you have to tell your customers is your cloud provider / hosting provider, then you sometimes have a separate provider for Object Storage (S3 or Backblaze), maybe another one for email delivery (Mailgun). You might have an invoicing/CRM portal (Stripe), SCM (Github), Chat (Slack), your own email setup (Gmail). And that is not even talking about any client-side tracking, things like Google Analytics etc. So it really makes sense to cut down the number of third parties, especially if there is any scenario in which they would be handling PII, and especially if you're selling to customers in heavily regulated industries.
I would like to use their hosted version, or a more stable paid on-prem version. Pricing is not the issue for me, but I don't want to introduce another third-party service and have to include that in compliance documentation for our customers. That is the reason I still self-host many things to be honest.