Why are there no new social networks?

Facebook has over a billion users. Literally. Something that big is not going to be taken down for a while.

There may be some around, but they just don't get the attention required to knock Facebook & Twitter off their perch.

Google's social network Google+ has been kept too low-key and not that too easy to figure out how to use.

Tumblr has been taken over by SJW "special Snowflakes".

I've created one with a PHP thingy called "Oxwall", but no one seemed to want to join 'cos they're all content with Facebook & Twitter it seems.

Creating a new one from scratch is freakin' expensive.......... programmers cost around $10,000

An off the peg "Social Engine" PHP script to create a "second string" social engine like MeetMe or Fubar costs around $299 (excluding extra plug-ins).... then you need costly dedicated server based webhosting to run the thing, as regular paid hosting on a shared server just won't cut it.... just having a website try to process 1 video is enough to put the server resources off the scale on regular paid hosting.... and it's a hell of a job these days trying to recoup the costs from advertising revenue these days with almost everyone using Adblockers

Facebook is the most convenient of them all

Google has hangouts and apps just like facebook.