First, those that buy extra chips are not necessarily expecting failure... Preparation doesn't mean you expect something bad to happen. It means you do not want to be caught unaware, should something bad occur. Some of us do not have an issue changing out a small circuit board. Rewiring an electronics test set that has a thousand white wires in it with tiny numbers to differentiate which wire it is (as opposed to color coding) can be a bit daunting. Swapping out a drop in chip is really pretty simple. Some people do not want to be out their mod for weeks/months waiting for a factory repair.
I have a Sig Sauer handgun, which is a really well made firearm. I have some spare parts (the ones more likely to wear out through use) for it, that have been sitting in a box for close to 20 years now. Considering the thousands of rounds I've put through it, I'm very pleased that I have not needed those parts, and it is a testament to its quality. It's not that I anticipate a failure, but I really do not want to not have the parts on hand to fix it, should I need them.
The sigelei 20W does look pretty cool. Too bad it has that same single button design. Were it to be multi-button, I'd probably be buying it.
The Single button is only used for firing the atty and getting into the menu. Once you are in menu you have to tilt the PV to adjust your power settings.