[cflsystems]

Because XC has way too much code using jQuery and going with a new version of jQuery every time it is released it's going to be a major pain from XC devs to check/update everything related to it.
So they choose the easy route of keeping this very old version because it works with the code there is.
XC has always been extremely slow at keeping 3rd party libraries they use up to date.
You can replace it if you want but be advised there might be issues here or there and with any 3rd party modules using jQuery as well.