It's possible that Sony didn't sell a sufficient quantity of that model of TV set to make it worth them purchasing the rights to stream ITV Player to it.
Many people don't realise that manufacturers have to pay for people who've bought their TV sets to be able to access 'smart' services. Several manufacturers have been criticised for withdrawing support for particular apps on their TVs only a year or two after purchase. (i.e. the manufacturer has stopped paying ITV, YouTube, or whoever, for the right to send data to the app on a particular model of TV, so their customers lose that service). It's possible that Sony decided not to pay to activate the ITV Player on your TV in the first place.
However, as Postdog says, it might simply be that you've not got the relevant app on your TV, requiring you to download it.
Phone Sony Uk Support on 0207 365 2810 (M-F, 0900-1800) for a definitive answer.
Alternatively, simply pay £9.99 for a Now TV Box to get BBC iPlayer, ITV Player, 4oD and Demand 5, together with YouTube, etc. (You don't need to buy any of the 'packages' that are on offer. You get the services I've mentioned without any further payment):
http://www.nowtv.com/box