You started talking about used gear by saying that you have "never" bought "any" gear secondhand. That sounds pretty absolute and across the board to me. Nevermind that you disproved it later conceding to having bought tanks and wetsuit used. BTW, tanks do require annual service. It all starts with the tank. If there is crud in the tank that blocks the valve or clogs the filter it isn't going to matter how good your regulator is. Hopefully, you opened the tank and actually inspected the interior rather than trusting someone's annual sticker.
To buy new or used is a personal situation depending on your knowledge and patience and what's available. Maybe you're hard to fit and have fewer options. Maybe you need it now and can't wait for the right deal. Maybe deals in your area are not as good. Maybe it's best for you to buy new but that's not a universal conclusion.
If you read back, I did not start out with the premise that everyone should buy their gear new. I had said that some gear is better bought new due to warranty considerations.
My reasons for adding the fact that I had bought a few items used and forgotten that I had was just to show, that at times, depending on the item and price, good deals can be available.
There's no black and white here of what anyone should do. There's a lot of grey and each should decide what is the best deal for them. However, it pays to be informed as to what the pitfalls are with going either route.
So obviously, I agree with what you have stated in your last paragraph. What I had originally stated, was that with the cost of what a second hand seller usually wants for gear, in my experience, and the costs of having it maintained out of warranty, oftentimes buying new is a better option than buying used for for some gear. However, that's just my experience.
Yes, I do know that tanks need annual servicing. However, they don't come with a warranty. In the case of my used tanks, they were only a short time out of VIP, etc. and I happen to know the person who did that work. My husband worked in the dive industry for 7 years. I do happen to know a thing or two about it.