IMO it is because SQL isn't a well liked/popular language (eg. the nosql movement) and it is a lot easier to avoid these days with all the various DBs. Personally I wish Prolog had gained more traction back in the day, it would have made a great alternative.

I'm thinking performance - it used to be a big deal to optimise database performance. Now most databases can live in memory so even if you're doing full table scans all the time it won't be that noticeable, and by the time the database has enough data in it that performance becomes an issue every one who built it has left.

The focus on micro services to, probably has an impact - the back end can be changed if your database is having issues and the services stay the same.

Also databases are hard and a large chunk of developers only know javascript and html.

You don't see many DBA jobs any more, a lot of that is moving to the cloud so they just pay more money and throw CPU's at the problem rather than optimise the database.

Also agile/scrum (as its practiced anyway) doesn't really allow for a database design up front as it used to be done.

I think it was:

1. The whole noSQL thing

2. A move away from databases as store of all knowledge to databases as implementation detail of applications, which IMHO was a good thing, but tended to make them smaller, simpler and more hidden away

If only those PhDs in the 70s would have though about scale out.

Prevalence of abstraction layers (ORMs), document stores, key-value stores, etc.?

Someone somewhere decided they didn't like SQL and engineered a way to postpone having to know SQL until their ORM performance dragged their systems to a halt.