Is it illegal to not cut your grass?

It's a violation of local city code to not maintain your lawn. The city will fine you if you do not cut your grass. You don't have to keep it super short, actually keeping it around 4 inches helps to block out weeds. Much longer than that though and it looks unkempt. Here the limit is 6 inches, and that varies by municipality. By the way, if you push it, there are a whole bunch of other things the city can be nasty about, stuff you didn't even think about, keep the grass cut and keep the city out of your hair, they can be really nasty if you don't

In some places you're required by city codes to keep your grass a certain height. Why don't you try a xeriscape yard, because you can have plants and ornamental grasses as high as you want. They're usually planted into a gravel base.

In the city where I live it's not exactly illegal in the sense that you could end up in jail for not cutting your grass. But there are bylaws in place that require you to keep your property groomed to a certain level. Now, I have seen some properties get pretty bad in some places, so I don't think anything would get done about it until someone files a complaint. But once a complaint has been filed, a bylaw enforcement officer may be sent out to investigate, and then take some kind of enforcement action where necessary. One standard consequence if the property owner fails to comply with an order of enforcement is the city will send out a crew to perform the clean up, or grooming where necessary, and the cost will appear on the property owners next tax bill.
I live in Canada, and by the time all of that might take place there will be 3 feet of snow covering the lawn, and the process will have to wait until the following spring.

Just try to keep your property looking good, don't cultivate any noxious weeds, and you should be OK.

Here you can be sited by the local government. You have to have special permits to allow the natural plants to grow up. Long grass also brings in all sorts of unwanted critters like snakes, and rats, and mice to name just a few. And if you still don't cut it, they will come in and cut it and charge you for it and it is very very expensive for them to do it and they do a lousy job.

If it's harming others or causing difficulties to other then yes and in some place there are some rules regarding the grass height.

If it's harming others or causing difficulties to other then yes and in some place there are some rules regarding the grass height.

If it's harming others or causing difficulties to other then yes and in some place there are some rules regarding the grass height.

If you live in an older subdivision, sometimes you can get away with not cutting your grass. But if you live in a newer subdivision, especially one with a home owners association, then cut your grass. You will certainly face fines if you don't.

Here in Orlando, Florida, it is a violation of the city code to allow your grass to become too unkempt. If you let it grow out of control, you'll first get a notice from the city informing you of that, and if you don't comply, they'll send someone to mow the lawn at your expense plus added penalties.

Never heard of such foolishness. Never had to mow my lawn before. Ever. Neighbors lawn is about 3 feet high right now. Home we bought last year, in the middle of town, has taken us 2 summers to reclaim the yard from grass and trees that overran the whole area. A lot of people let their lawns go just to cut it down for hay for the farmers.