Why Centos still not using Latest kernel

CentOS 6 is based on RHEL 6, which was released in 2010. Within a major release, the goal is compatibility and not introducing breaking changes as the target audience is enterprises that value stability over features. As you can see from the version history, they don't introduce new kernel versions within a major release (but some fixes are backported), so it's likely RHEL 6/CentOS 6 will stay on 2.6.32 (a stable kernel version).

To get a newer kernel, you'll have to wait for RHEL 7/CentOS 7 and upgrade. It will include kernel 3.10 (another stable kernel release).

Since Red Hat supports each release for 10 years (or 13 with extended support, e.g. RHEL 6 until 2023), it's no surprise they don't release a new major version every year.

There may be a disconnect here.

CentOS, like any enterprise linux, is geared toward stability and, importantly, compatibility throughout the major release (review Semantic Versioning).

In order to maintain compatibility, software released within a given major release will not suddenly be revised to a completely different baseline. In addition to breaking any kind of certification in the upstream distro (RHEL) with ISVs, the nightmares in (in order) testing and then support will create an untenable labour issue for anyone trying to actually support it.

If you need last week's code drop, you may want to consider a project with a release cycle more like a mayfly and less like infrastructure. Your upstream and downstream support will change dramatically, and consistently delivering a product may become a moving target, but this may be a great experience. Maybe look at this month's Fedora, or whichever mubuntian deriv is fashionable.

EL8 will of course have a newer kernel, and you may want to use Fedora in your test environment so that you can properly release on EL8 when Fedora's promoted to EL.