You can change the activity to cycling in MFP, and it may run that through some sort of algorithm, based on your entered weight, but it's not going to be all that accurate, might even be off as much as +/- 30%. Most people get steps data from a watch or phone, so most have GPS and they can figure out your "steps" are not walking, it's doing some other activity.
It's more accurate using a heart rate monitor and some sort of GPS unit as it can combine that with your weight and "sort of" figure out your power, as it will know the route/ elevation/ incline/ decline roughly etc, or average that out, it's going to be a lot more accurate, but not as accurate as a power meter on a bike or on a turbo trainer or something. But then even that isn't as accurate to being hooked up to all kinds of machines etc. Different bikes and different riding positions could appear to be more "power" but in fact aren't, like on a TT bike, you're a lot less wind resistant, so you can go much faster for less power/effort. Same applies with different tyres or riding inefficient bikes or whatever, and like on strava it will estimate your power differently depending on what ride you do (road/ MTB etc).
For me, I tend to be averaging 900 cals an hour when out on the road bike, based on HRM and GPS, and estimated power, but in MFP I'll enter it as 600 an hour, or just add on 300 "calories" to offset some of it, when trying to lose weight.
People can go thinking they've burned 2000 calories, and then go and eat 2000 calories, when in fact they've only burned 1200, so now have an 800 surplus. They get fitter, but no less fatter (not factoring that people can get slimmer at the same weight when gaining muscle and losing fat).
