Why does ubuntu 14.04 LTS not see skins?

Question

linux

Installed ubuntu 14.04.
worked for 3 days.
put nginx, php, mysql.
The theme of the design changed itself, I wanted to switch to the default one, it did not work out. only HighContrast is displayed in the system parameters and that's it.
in the /usr/share/themes/ folder there are all the themes that were in the assembly

drwxr-xr-x   3 root root  4096 апр.  17 07:23 AgingGorilla
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Atlanta
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Bright
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Crux
drwxr-xr-x   4 root root  4096 апр.  17 07:23 Default
drwxr-xr-x   4 root root  4096 апр.  17 07:23 Emacs
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Esco
drwxr-xr-x   5 root root  4096 апр.  17 07:24 HighContrast
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Metabox
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Raleigh
drwxr-xr-x   3 root root  4096 апр.  17 07:23 Simple

Answer 1

Because half of the applications are on gtk2 and half are already on gtk3.
HighContrast and a couple of themes have already been converted to gtk3, but most of them are outdated.