I genuinely don't think many have thought that far ahead from what I hear from people I speak to and the shite I consume on Facebook. A majority are still happy to be at home and want more of it, mention money, it doesn't seem to have registered it'll all need clawing back.
At least in my pool of contacts, I think the reason is simply phones have reached the peak of what they can offer. People can do everything they need to, and they can do it SIM-free. My current phone from EE is unlimited minutes/text/data for £28 a month (ex-VAT). Another is about £14 for unlimited minutes/texts and about 20GB of data. A phone that does everything Joe Public wants to do is on eBay for less than a hundred quid. Gone are the days people are willing to sign up for 3yrs and pay £60 a month.