Problem for phone companies is that, say 10 years ago you got a free phone on a 12 month contract with the phone being worth about £100 or os, and they took the cost of that for you. Then phones got cameras and were costing O2, Vodafone etc more to buy, so they put on 18 month contracts so they could recover the costs betters. Now a mobile phone is everything from a web browser to a movie player and costing a lot more, they need 24 month contracts.
Simple answer is get the most simple phone you need.