You see a ZTR from a distance but you don't see what the operator is doing or how it has been modified.
You also should have noticed they were not mowing with an Ariens Ikon, for very good reasons .
Contractors use ZTR's because they can mow faster with them and time is money, that extra 1 or 2 lawns a day is a lot of profit at the end of the season.
They just weight up the risk vs the profit .
I have modified a few ZTR's so they will work on customers lawns including fitting bigger diameter wheels , wider wheels, square shouldered tyres and tyres with a more open tread , a lot counter weights and solid front casters.
All of these were so the customers can mow slopes steeper than the mower was designed to cut on.
I have also replaced a dozen or more engines because the customer was mowing slopes steeper than the mower was designed to cut .
ZTR's are carefully designed to have 10-20 lbs of downforce on the front casters constantly.
When you shove a bagger on the back that reduces the downforce which allows the mower to wander so wheel weights or foot board weights are added .
However the problem is the amount of weight from the bagger is constantly changing so when it is empty the caster wheels will tend to dig trenches in soft grass and when the bagger is full, particularly with ( mainly men ) people who compress the grass in the bag cause they only have 1 or 2 more runs to do the down force on the front wheels can be less than 0 .
This tends to play havock with the bearings on the axel & the pivot unless it is a commercial mower with tapered roller bearing .
It also tends to bend the caster yokes which makes the mowers really difficult to steer.
When it is all said & done, it is your mower , your yard & your body so you have to make up your mind as to what you want to do with it and how much risk to both the machine and yourself you are willing to live with.
We have all been brainwashed into believing that a garden is a massive mill stone around our necks that will cost a fortune & consume every free second of our time and lawns just take care of themselves with minimal effort when it is the exact opposite .
Down here real estate agents will get people to bulldoze their garden & replace it with turf because that will add at least 20% to the sale price and make for a faster sale which from what I have seen locally that would appear to be correct .
Just about every one of my customers have increased the amount of garden & reduced the amount of lawn following suggestions from myself .
Every one of them never stop thanking me for making them aware that gardens are lower maintenance than grass .
Many of them who were formally slaves to their property are now enjoying it
Those who used to bag now mulch except for the ones who became very keen gardeners who catch in order to make mulch & compost