Level editing tools are created to build the levels by the devs. They just don't want to give them to players because they want to sell you additional content.

Talking specifically about the usual suspects but hell, even some indie games are doing it now, in indie games it seems more popular to release a new game entirely which is basically 1.0 with new maps but thankfully there are tons of passion projects that get new content for years and years who really deserve more support.