It is entirely possible to drive in each day. It's more that there's no free parking. There are several car parks on campus, but parking can get expensive. There are passes you can buy, and there's supposedly a carpooling scheme to give you a discount (although no one ever seemed able to find out anything about it).
Most second years live out in Leamington or Coventry (or the little towns nearby such as Kenilworth or Earlsdon), and the buses are so horrendously bad that many people drive in. This means that there are a lot of cars around on campus and it's no joke when I say that you're sometimes driving around for over an hour in the morning trying to find somewhere to park and end up parking near the restaurant on the far edge of campus just to save your sanity. Needless to say, making a 9am lecture is quite an achievement when you're in second year, especially in term 1.