Also whats the problem with using windows xp with a limited account. A lot of security problems happen because most windows users use an administrator account which allows anything to install any way it likes.
The main issue is that it's not very usable. There is no simple way to quickly switch accounts (There is fastswitch, but that only helps so much). So whenever you want to install a new program, you need to switch to the admin account, change certain settings, switch to the admin account. Another issue is that particularly for businesses, is that if they are remaining on XP for using certain software, sometimes the reason they need XP is specifically because of user-permission issues, so now certain programs need to be run as admin. And of course many users are sticking with XP because programs they use only run on XP, and usually that is because they don't work for limited users (eg. under UAC on Vista/7/8) and running as a Limited User on XP will cause the same problems.
What usually happens is even the most dedicated user will find the micro-management and hassle of switching back and forth for certain programs running as admin and those not too much of a hassle and will just run as the user that everything works with.