Say what you will about SQL databases and I'll probably agree with you. However, larger organizations have to think at a much larger scale than the typical startup does. Migrating from a SQL database to a NoSQL database is a much more difficult decision to make once you reach a few hundred thousand lines of code, much less millions.

And I haven't even gotten into the logistical issues yet. Do we have server capacity for the new database? Do we have people who know how to administer the new database? Can I install it in under a month on our server running <insert outdated version of RHEL here>? And these questions become doubly important if your clients are running your software on their own servers. Now not only are these logistical issues, they're excuses for your clients to drop you and go with someone else.

To make a long story short, if NoSQL databases are worth it, enterprises will get there. But it's going to take a while. Much as us engineers hate to admit it, that might even be a good thing.