Why most of the web hosts using old processors?

[Jordan]

Shared hosting isn't all that CPU intensive. You're probably going to reach a disk I/O bottleneck before you hit a CPU bottleneck. Is this always true? No. But I suppose my opinion is that expensive bleeding edge CPUs is mostly wasteful in a typical shared hosting environment.

Servers with bleeding edge CPUs are going to be much more expensive. In order to make those cost effective, you're probably going to have to cram a bunch of hosting accounts on that one server. Then all of a sudden that hosting company has all of their accounts on one server - a single point of failure. And it also makes it more difficult to recover from backups in an event failure (restoring 200 accounts is a lot faster than restoring 6000 accounts).

My preference would be to have many small servers with few accounts spread across, rather than dumping all of my eggs in one large basket (or a few large baskets).