If you get someone to mow your lawn, do you not care if (a) they use an automated machine that you could rent by the hour for far less, and/or (b) at the end your lawn is actually in a good shape?
If the lawn looks great you get to do it again. I could ask the guy you send how much you are paying him and I could ask you how much the mower costs but it wouldn't necessarily be a good use of my time.
And conversely, say that the person or machine that you paid to mow the lawn instead drenches your yard in herbicide and then salts the earth. Or vice versa, it starts planting weed seeds, or brings a bunch of ticks in the grass etc. You would probably not be happy to let this process finish and then say "oh well, guess I won't be hiring them again!" and just move on.
If I'm getting a $200 mowing bill it could be worth looking at the machines. If I pay you $4 per week I wouldn't worry about it.