The comments above about fighter pilots needing their HOTAS to control only those things that they need to get through combat alive and GA pilots not needing anything on their stick or yoke are valid. However, for those of us without a life-or-death combat requirement, I do not see the harm in putting some workload-reducing buttons in convenient places like the stick.
For those who debate whether "ident" is important enough to go on the stick, I think it's a very local decision to make. When I got a week of aerobatics lessons at KCHD, I think Tower asked us to ident every single time we called up to re-enter the Delta airspace. If I were based at an airport like that, I would put the ident button someplace I can find it without looking down when I should be scanning for traffic. But in my normal flying, I get asked to ident so infrequently that I would not want to waste a wire, much less a precious button, on it.
On my RV-14, I may have gone overboard with buttons on the stick, but I'm happy with what I have. I have a 2-axis trim hat, Comm 1/2 swap, Comm frequency swap, PTT, A/P disconnect, and Smoke on/off. The frequency swap works on whichever Comm radio is set to transmit, so I can stage up to 4 frequencies that I can switch between without having to use the touchscreen and it is intuitive that the buttons that control a radio (frequency swap and PTT) always target the same radio.
I thought about putting the starter on the stick, but in the end decided I can hold the stick with my legs to get the plane started once per flight. I put flaps and TOGA on the panel near the throttle. If I had a fancy throttle quadrant, I would have put a button or two on the throttle handle instead of the stick/panel. PTT, for example.
I also put PTT buttons on the panel for the pilot and copilot. Sometimes, the person (or autopilot) flying is not the same as the person talking on the radio, and I wanted to let the radio guy talk without touching the flight controls. I also put a stick disable switch on the panel, which some people call a "grandchild switch" because it disables the PTT and other buttons on the copilot stick. I wired mine work to disable either stick (with a middle position that enables both of them), just in case I have a wiring fault on the pilot stick. I did all the wiring myself and know better than to trust its perfection.
So...is that overkill? Maybe, but I have over 100 hours and almost 150 landings in the plane, including about 10 hours of IFR cross-country flying, and I have not found any of it to be obstructive to simple, safe flying. The only thing I would change on the stick, if I could, is to ditch the smoke system (which I still haven't figured out a good plumbing route for, so I haven't ever used that button except to test the control circuitry) and use the button on the stick as a Bluetooth pause/resume button for the GMA 245R audio panel, a feature that I have requested Garmin add but they haven't as yet. I listen to audiobooks and it would be great to be able to pause them without keeping the audio panel page or my phone in front of me at all times, so I don't miss exciting parts of the story when ATC wants to chat.