Buying from a carrier makes no sense to me. In the old days it was the way phones were bought when you had less options for carriers, but over time it became clear that it wasn't worth it. When I did the math, I found that the phone comes out barely any cheaper (if at all), and the trade off is that you cede the option to change carriers or downgrade your plan for the next two years.
So if something goes wrong, your carrier is unreliable, something happens with roaming charges or whatever and you get a big bill for something that shouldn't have been charged to you, you don't want to be stuck with that carrier and without a contract you have the leverage of threatening to walk away if the problem isn't remedied. And of course, there's the phone not being carrier locked so you can decide to sell it after five days if you want to.
Since I don't have these issues, the main benefit for me in avoiding carrier subsidized phones is that if I am out of contract, my carrier will call me with offers of various discounts just to get me to sign a one or two year deal (if you bought a phone from them, you don't get this as the phone is their end of the deal, you're already locked in so they have no interest in giving you incentives to stay). This way I get some services for free, like for instance at the moment I am approaching the end of my two year free subscription to Tidal, which meant not paying for Apple Music or Spotify for two years. Very simple math says I come out way ahead since no carrier deal can net me the savings I got from having free music streaming. In fact it's been so long since I paid for Apple Music that the Music app has already offered me free trials three times over the last couple of years, each time offering one or three months for free.
From what I can tell, carrier deals are good for two types of people - 1. those who don't qualify for or simply don't (want to) own a credit card, as they can do a payment plan for a phone they may not afford or want to buy outright, and 2. those who have ginormous phone bills due to a lot of calls and texts so these people get excellent deals for more expensive phones as they will pay them off through their massive carrier traffic anyway. But I guess no. 2. is on its way out, since these days you will easily find carrier plans that give you unlimited pretty much everything even in the mid-tier plans. I have such a plan with my carrier and for 20 euros everything is unlimited, and the only thing that is technically constrained is the internet traffic, which is 60GB at max speed and then it drops off to unusable speeds, but you're still online as the internet data itself is flat. I can't even take full advantage of this since I have Wi-Fi so I'm interested in seeing what the carrier will offer me next as my contract is up in four months and my Tidal free subscription ends.
I buy my tech either through my company (self-employed so it's a tax deduction) or on a payment plan through a credit card with no interest. I find it completely unnecessary to pay for tech outright unless I'm going through my company, since no interest on my credit card means I am not losing any money, I am just defering the payment until later, and given how money loses value over time due to inflation and whatnot, technically I can even come out a little bit ahead if the payment plan is for two years and some mental midget starts a war that explodes world trade and inflation along with it.