The thing is I only picked on forms off the top of my head. There's a ton of functionality in your average client site which I can't imagine JAMstack catering for without it costing a lot more than hosting it on a VPS. JAMstack seems to cater for the painting by numbers model of web development but that's only a small fraction of what clients need. The JAMstack equivalent of a typical WordPress site, I imagine, would have to pull-in a dozen external services costing a lot more than the VPS alternative. Netlify make a big deal about the low-cost scalability of the CDN factor in JAMstack but it's only low-cost when you don't use external services. It's quite the opposite, I've heard, once you've outgrown static and need a third party service for every new feature.