I bought a Pixel 6a earlier this year, and traded in my Pixel 3a for $150 USD off the $300 sale price. Other than the fingerprint reader being kind of terrible, it was worth it to get a new battery and OS updates for the next few years for $150 (plus tax and shipping).
If you don't want to spend a lot on a phone, you can do that.
It's true, and my partner got a free phone by switching to Fi. My switch was just ill-timed... I tried out an iPhone on a new carrier for the first time, and hated both so much I paid to get out of the contract and start a new service with another carrier and Android again.
If you don't want to spend a lot on a phone, you can do that.