Data really doesn’t back that up. Adjusted for inflation it’s cheaper to get lawn care done today than 40 years ago. Minimum wage was actually higher back then and automation was worse. Landscaping is extremely common with industry revenue hitting $51,908,304,000 in 2016 or an average of ~400$ per household per year across the US.
In the case of lawn care specifically, automation that requires some capital beyond what may be worth it for an individual probably helps. I have a lawn service and a small crew shows up every two weeks with various gear and they're out in 20-30 minutes.
That said, I'm not sure how common getting a lawn service is among middle to lower-middle class households is.
And I'm pretty sure most middle class-ish households don't outsource all yard/garden work generally.
In my part of the US, even in an upper middle class suburb, most of the people in my neighborhood do their own mowing and edging. I hate mowing so I’ve actually priced out lawn services and I just can’t justify it. About $40 per service (for a fairly small yard) at 4-5 times a month adds up.
I think in the US, there's often a bit of an attitude too about people doing things for you that you're perfectly capable of doing yourself. In this case, I justify it on the grounds that I usually travel a lot and, especially in the spring, the lawn does need to get cut regularly. But I just get it done every two weeks. That's on the long side in the spring but it works for me.
More of a luxury for me is having a housekeeper once a month although it's nice to have someone give the house a good cleaning now and then. It's totally unnecessary with me not traveling at the moment but I wouldn't feel right about canceling them.
Gardening is something of an exception specifically--although even there, there are landscaping projects that aren't necessarily "gardening." But, while some people do just like an excuse to get of the house and do some outside work, generally people are happy to have their lawns cut, leaved raked, brush cut, trees trimmed, etc.