Actually it makes a lot of sense. Some of the reasons include:

- Stable\known CPUs, most vendors are used to Intel.

- Infrastructure\Support, Intel has a lot more infrastructure to support customers\contracts

- Long cycles, servers are more complex to replace and contracts can span multiple years.

- Compatibility, many rely on Intel specific features or are afraid to try their solution on a different CPU vendor.

- Relationships\Market Share, Intel still is a far bigger brand with more prestige