Why are servers running python 2.7?

Question

MODX

Hello. I repeat, I don’t remember what time that python began to study not so long ago, and such a question arose.
I have access to 5 different servers, and all of them are running python 2.7, I can't understand why, if there is a 3.x version?
This question is due to the fact that I work on a local computer and installed version 3.6, and on all servers the version is less than 3. And it turns out that if I transfer my code to the server, then it will not work correctly there? (I read that the second and third versions have different syntax).
And in order for everything to work well in the future both on the local and on the server, you need to roll back on the local to 2.7?
I immediately apologize if the question is too stupid, but a quick google did not give a clear answer), Thank you!)

Answer 1

So not all configs, carefully check again, 4 config files. It looks like the path is still wrong somewhere.
Just in case, check .htaccess, it can be disabled for launching if it was enabled.

Answer 2

Because python has been shipped with most Linux distributions for a long time and some of the utilities are written on it. It makes no sense to rewrite them under 3x.
Now type in Google "python virtualenv" and you will be happy.