Using CE Router for Internet and VPN services

[Akhmedd Aly <akhmed.aly () gmail com>]

Hi,

can someone explain me why service providers (Internet and/or L3 VPN
services) obligate customers to use CE routers. Why they cannot
configure more than /30 (in some cases /31) subnet mask on PE
interface side for me? In that case I can use cheap L2 switch and use
default gateway on all my PCs in the LAN, pointing to SP PE.

Please describe all benefits and detriments of using more than /30
subnet on SP PE.
Some good links will be very useful for me.

TIA!

--
AA