don't understand the question. Prop-driven airplanes have a primer,
throttle and mixture (choke) control on each engine.

Ok, I try to make it VERY simple!

In 1971 my dad bought a store brand mower.

to start it all you had to do was set the choke to "start" and pull the
starter cord.

in 1986 he replaced that with a Sears mower.

It had a primer bulb that had to be (as the manual said) "pushed until
firm."

I just want to know why if a 1971 mower did not have a primer bulb, why
should a 1986 - today mower have/need one?

And why does Honda mowers don't have/need a primer bulb (by they do have a
choke).

P.S.

Of course I could make life simple, and pull the 1966 reel mower out of the
basement :-)