The thing with projects is that you have to deliver it in time and the client doesn't really care what you did behind the scenes as long as you have the product ready and working on the release date. Sometimes, adding new tools to the project might seem a bad idea, especially when the team is not up to speed with the latest trends.
Not everyone works in a team which has the time and resources to spend on trying out new stuff on each project.
Some people are not really motivated, don't have the passion or the burning desire to learn it or work with yet another tool. Saying "I want to do this" and actually doing it (or at least start somewhere) is different
Me personally, I want to experiment with a lot of tools and technologies for projects and even promote stuff for usage / giving ideas but it's not as simple as "OK let's do it right away", it takes time.
Remember that you add a lot more complexity for each tool or technology you use. While it helps you solve a problem easier, it takes your energy faster. The same can be said with architecting applications like they are huge like Amazon but it ends up being a mainly CRUD app.
There are probably a lot more reasons for it but these are the ones that come to my mind first.