It is happening though internally in businesses I've worked with. A few of them are starting to replace SaaS tools with custom built internal tooling. I suspect this pattern is happening everywhere to a varying level.
Often these SaaS tools are expensive, aren't actually that complicated (or if they are complicated, the bit they need isn't) and have limitations.
For example, a company I know recently got told their v1 API they relied on on some back office SaaS tool was being deprecated. V2 of the API didn't have the same features.
Result = dev spends a week or two rebuilding that tool. It's shipped and in production now. It would have taken similar amount of time to work around the API deprecation.
> It is happening though internally in businesses I've worked with
How many samples do you have?
Which industries are they from?
Which SaaS products were they using, exactly and which features?
> ...a company I know recently got told their v1 API they relied on on some back office SaaS tool was being deprecated. V2 of the API didn't have the same features ... dev spends a week or two rebuilding that tool
Was that SaaS the equivalent of the left-pad Node.js module?
I know of at least two multi-billion corps that are moving to internal ETL tools instead of 5tran now because the cost to maintain internally is much lower and you can customize for cheap. SaaS as a model is at risk without something tying someone down.