Well it’s not the same, it’s more like a car manufacturer insisting that you have your car serviced at an accredited garage during the warranty period. Imagine the up roar if they did, oh wait.
Not really, because it isn’t anything to do with the warranty, and the warranty period on a few phones is way less than the contract period (Apple are bad for this).
If you’re in the contract period you have to pay whatever you contracted to pay. The locking of phones is in theory to make it more compelling to you not to just stop paying and let them sue you. In reality, it is just a way of them trying to ensure that you stay with them by holding your phone to ransom. That’s why they offer you a ‘free upgrade’ slightly before your contract is finished, to lock you in again and in order to make you think that you have to keep with them.
And because the phone is subsidised by the phone co.
If you bought a cheap car on the basis it was part paid for by shell…
True years back in the olden days of extremely high phone charges. Nowadays, if you look at the difference in cost between sim only contracts and phone costs, for most high end phones, you end up paying roughly the same for the phone, there is very little subsidy, it is just an extended hire purchase of a phone. In some cases (Nexus 4 being the obvious one), it is actually cheaper to buy the unlocked phone and a sim card separately. So that justification is a lot more shaky nowadays.
Interestingly t-mobile USA just announced that they’re not locking phones, they’ll just sell you a phone, and sell you a sim package. You can hire-purchase the phones if you want to spread the cost, but they are getting rid of a lot of the opaqueness that is inherent in the ridiculous system of ‘upgrades’ and ‘free’ phones.