The reason why is that there will be no more security updates for those Operating Systems. Say a critical issue is found in XP. Microsoft is under no obligation to patch that and you be exposed unless some third party patched it (unlikely) or you upgrade to Windows 7/8.
MS Releases security updates almost daily so it's not unrealistic to see that happening. Strongly recommend you make the move. Obviously, you don't have to do it all at once. Some people are looking into cloud or "private cloud" instead of buying new desktops/upgrading/servers. It can be a lot less hassle and a lot cheaper. Nowadays, it's frequently the case where we have more processing power than we actually need. Even in my office, employees hardly push a i5 processor past 10%. This is what cloud providers capitalize on but you can do it in your own office too.
But it's not for everyone like power users who use a lot of resources. But these people are the minority
.png "ACUF Donor I")
