SaaS vs Open Source tradeoff?

Software projects are often a mix of proprietary and open-source components.

For example, you might be running Python (open source) with Flask (open source), Reddis (open source), and React (open source) on AWS (proprietary) with a managed instance of DynamoDB (proprietary), processing credit cards with Stripe (proprietary), and gathering analytics through Google Analytics (proprietary).

Every proprietary option except Stripe has open source alternatives:
AWS -> Open Stack
DynamoDB -> MongoDB
Google Analytics -> Matomo

What is your motivation for choosing a proprietary managed option over the open source alternative? Do you worry about data privacy / vendor lock-in? Conversely, do you worry that the open source solution would be more difficult to deal with?

What is the tipping point for you?

I ask because I am building a proprietary SaaS computation framework, https://fastmap.io, but am getting feedback that suggests that there is real concern of lock-in and/or data privacy. I am considering open sourcing it to alleviate these concerns but am trying to understand my market better first.