UK businesses tend to purchase vehicle tracking outright rather than with leasing or contract options. There are definitely advantages to buying the system with a full payment. You will save money on the costs and for companies with a lot of cash it is a very sensible option.
There are disadvantages to this option though. Technology does not stop for anything, even fleet tracking. Tracking manufacturers can get bought out and customer service can change over time. For these reasons and more it can be beneficial to have a contract for 12 months to see if you want to trade tracking companies. Once you make that large investment on the complete system you will probably not want to trade companies. With a contract commitment it is easier to lease if the company does not suit you.
These contract options or pay as you go choices provide a short term contract where you are committed for a small period of time with the eventual choice in staying with the same company. The payments are higher, but you tend to be better in the long run. There is definitely more flexibility with a contract over buying the product outright.
Large businesses have opted for short term contract deals because of the reasons stated above. They understand the numerous benefits to having a shorter term contract. You do have long term contract options too, but again there is less flexibility making the short term option more appealing overall to businesses.