That is a very good question and when you compare Honda lawn mowers with other brands, the reasons become pretty obvious.
The biggest reason in my opinion is quality. You are going to pay a little more for a Honda lawn mower, but I have seen them come into my small engine repair shop that are more than 20 years old. You won’t see many other brands that will come even close to lasting that long.
Honda starts out with a very dependable engine. Their self-propelled and push mowers typically use a GCV type engine in 160 or 190cc. This is plenty of power to mow your lawn and pull the mower up hills easily. As long as you keep the oil changed and do the required maintenance, these engines are pretty bulletproof.
The decks on a Honda are either steel or plastic. Both of these are pretty rugged and the steel decks will almost never rust through. As long as you keep the deck scraped of the wet grass buildup, rust will not be a big issue.
The controls are pretty intuitive and are built fairly well. They require some lubrication and maintenance and the cables will go bad in them just like any other self-propelled or push mower.
Drive systems are a big one and Honda spares no expense here. They use steel on steel gears instead of a steel drive gear and a plastic mating one on the drive wheel like a lot of competitors.
Honda uses a Twin Blade system on some of their mowers. This cuts the grass very fine and helps to mulch it as well. This is another plus to a good looking lawn.
All in all, Honda puts quality in every aspect of their lawn mowers and it is money well spent to keep your yard looking great.