Most vendors make it so hard to handle that defaulting to chargebacks is sensible (at least when the charge reasonably qualifies -- the kid with a parent's card example doesn't seem appropriate).

If a vendor makes a $20 oopsy, it's not worth the vendor's time or yours to track down their phone number, find that just the phone number section of their website is broken, acquire it elsewhere, see that it recently changed or is otherwise no longer in service, go to their website and interact with the cheapest chatbot solution they could find which somehow costs more than unfiltered Sonnet 4.6, be greeted by 3 help pages which have literally nothing to do with the problem at hand, go through the entire dialogue tree and see that it's useless, ask to be connected to an agent, which spawns a secret dialogue option informing you that you can call 555-5555 to speak to a human being, sit and wait for a voice prompt recorded at half-speed which feels the need to repeat every single choice and interaction back to you, navigate the entire phone dialogue tree, try various permutations of "representative" and swearing to see if there's an escape hatch, be redirected back to the website, ... <magic> ..., somehow eventually connect to a real human being, have your request denied, go back to step one and find a better informed representative, have the charge reversed, notice that the reversal hasn't applied even a month later, go back to step one, find a representative who will actually press the reversal button instead of just saying they did to juice their metrics, and come back several more times over the next year as an automated system repeatedly flags the associated purchase as not being paid in full (since the charge was reversed).

Or...I can send my bank the timestamped dashcam footage of me entering a parking garage, their prices and policies, and me exiting the parking garage, tell my bank what the right charge should have been, let the garage dispute that if they really think I'm wrong, and wind up having the entire charge reversed instead of just the delta I asked for.

I'm sure your vendor is one of the good ones, but my tolerance for bullshit from the rest is pretty low nowadays, and I won't finish going through the official process if it's too onerous. Somebody got a pat on the back saving $5 for the call I never successfully placed, and the business lost $20 on top of the actual refund in chargeback fees.