Having had the pleasure in training three kids how to ride a bike, forget training wheels, or taking the pedals off!

find a reasonable long grass hill - not to too steep, but steep enough to allow a kid to go down the hill riding the bike with out pedalling.

and then goto the top of the hill and let them go down the hill on the bike. Once they master the balancing part of going down, they seem to pick up the art of turning the pedals at the end of the hill to keep going (if not, explain what to do)

advantages: doesn't hurt when they fall off, gets them used to rough terrain. it becomes fun once they start to master the balancing bit

We did exactly this for my first son.

We had been trying for weeks without result, both with trainer wheels and to run behind with an attached handle. Then one day we unmounted the pedals and lowered the seat... after just an afternoon we could reattach the pedals and he was now cycling on his own!

I did this with my daughter. She was riding her bike within the hour. I made a game of it with chalk on the street. She how far she could glide, then mark it. Keep repeating... Eventually put on the pedals, and off she went.

It’s much easier to add and remove training wheels than mess with an integrated part of the design.

Eh? They are bolted on with screws and get regulary replaced. It's not any difficult than removing training wheels.

Nope, thread starter has a point here. It's not only pedals and screws. You probably would like to remove the front gears and therefore the chain, that requires you to remove the whole rear weel. What if you have a back-pedalling brake hub. Besides that now you have a "hole" in the gear area, maybe full of oil, Also the bike designed to perfectly run with the full gear on. And so on... you may not want to tamper that "perfectly" aligned system if your kid is playing with it. Nope...it's not just about removing the pedals.

Or just remove the pedals and tape one of the cranks to the chain stay so they don't spin and catch the trousers. Did this with my daughter's bike and it held up fine for the month she pootled on it until she was ready to pedal.

Why do you need to remove any gears? You just unscrew the pedal from the arm and that's it.

I'm really not understanding why you think it's necessary to remove more than that.

I've done it on quite a number of different bikes, it really is quite easy.

You'd think so, but having taken apart a couple of bicycles I gotta say it's far more complicated than say taking apart a PC. There are so many seemingly pointless steps involved like removing C clips that don't belong and solving some topological problems to get the chain out. Notice how the chain and the triangle frame are interlinked.

I have no idea how these victorian steam punk contraptions are assembled and sold at a <$100 price point

Are you maybe thinking about cranksets? All it takes to remove a pedal from the crank is an adjustable spanner.

Define "regularly". I've replaced pedals on bicycles I've owned exactly once in my lifetime. That includes the 4 year period prior to COVID that I commuted by bicycle and caltrain. It was much more difficult to loosen the bolts and get them re-fastened than the training wheels on my oldest's bicycle. Not to mention the handling of the chain.

I switch between toe clips(for commuting) and cleats(for longer rides) at least once a month. Why would you need to handle the chain? Pedals are attached to cranks.