You and just about everyone else does. If you have a decent connection you will pull host just about every time. Just don't be like 70% of the other users and try to manipulate your connection to avoid being host, it just makes matters worse for everyone.
If you can get into your router settings switch off upnp, this does not mess up other peoples games but it will stop you from getting host all the time. You will still get the odd game as host but nowhere near as often.
That should give you a moderate / strict nat, unless you have a dmz setup or manually opened up mw3 ports in your router settings. In gaming generally it's best to have an open port, for mw3, not so much do to lag comp and the hosting situation.
I have a dmz setup because even though in modern warfare 2 and black ops it said my nat type was open I couldn't connect to other strict or moderat nat types so I put it in DMZ and now I can connect with them.
They either make me host or they pick a horrible host that gives everybody lag problems (3 bar at best) and lag spikes. I rather be the host atm, but that can go shi-t fast too. I love being a client 4 bar player in a room full with 4 bar players..