Buying a phone using installment (translate added interest) is a no-no because phone depreciate from the start of your purchase. So you are paying extra for something that is already depreciating.

Because not everyone can fork out a lump sum to buy a car. If one is capable, please to do so as well. Phone is different, can't fork out a few thousands? just bloody save the money. Plus when you finally manage to save up the money, the current price for that new handset might already drop as well which doesn't apply to cars. Car price dropped year end true but car also depreciate more straight after purchase by the end of the year, so bad second hand value (pros and cons but let's not dwell more into the details coz the thread is not about cars). Worse come to worse, just buy a cheaper phone which you can afford if you desperate needed one but a cheaper car that you can "afford" is still at least 30k or so, which is a big sum for many people.

You picked a rather incorrect analogy to justify purchasing through installment.

HAHA... yeah I get what you mean, don't mean to come out harsh on you. However, the feeling of "want" is pretty much spontaneous in nature. If one have the money to burn for that "want", fair enough. However, having to bear the cost of that spontaneous feeling with debt that you have to repay in installment might be a price to high to pay. Well that's the angle viewing from, anyway. Pretty boring huh?