Okay, so, I edited your question to make it more general, but...
To answer your issue specifically, in which you use the INIZ VPS provider (based on pre-edit version of your question):
I did look up the VPS provider you said you used (before my edits to your question, so it's more general) ,the INIZ VPS provider.
They have two solutions listed on their site: VZ solutions (Budget VPS and SSD VPS), and KVM solutions (KVM VPS).
I am assuming that, in your case, you have a Budget VPS or an SSD VPS from INIZ. That uses the OpenVZ solution for virtualization, which means the host system has a 2.6.x kernel on it, and that's what your system sees.
Now, for a more general explanation of this problem, and to answer your question fully:
Depending on the VPS provider, and the virtualization system being used (OpenVZ, KVM, XEN, etc.), the kernel that is on the VPS is either that of the host system or is a kernel installed inside the VPS.
The three biggest ones I've seen are OpenVZ, KVM, and XEN, so I'll talk about those three here, however, there are other virtualization systems out there, but I don't know about those.
With OpenVZ VPSes, the kernel that the VPS sees is the kernel that is on the host node, which in this case is running 2.6.x kernels.
With KVM VPSes, the kernel for the VPS is the kernel that is installed inside the VPS, and that will be, for Ubuntu, whatever comes with 13.04 or 13.10 or whatever.
I did discuss with my friends who are heavy into virutalization and stuff, they said that for XEN VPSes, XEN can be configured one of two ways:
- with ParaVirtual Ops, which means the VPS can have a custom kernel inside it (i.e. what comes with Ubuntu or a custom kernel you compile)
- without ParaVirtual Ops, which means the VPS will have the host system's kernel exposed and used with the VPS. (similarly to OpenVZ)
(These same friends confirmed what I said above about OpenVZ and KVM, as well)