You make the rule such that if you can sign up for a service on a website you can also cancel it said website. Now your hypothetical landscaping company is safe
Are they? A very basic website can easily have a form you can fill to sign up and all it does on the back end is send an email with the info to the proprietors. Even a generic mailto: or tel: link arguably makes it possible to sign up via the website, if tapping the link on your phone to send a message can directly result in a signup. To do the same thing for cancellations you'd have trouble avoiding the need for customer accounts to sign in and connect to a database to list what services they're currently subscribed to etc.
Otherwise people who signed up under the wife's name may try to cancel under the husband's name and you don't know who they are, neighbors who don't like the racket from the equipment see your website on the trucks and try to cancel the service even though they're not the customer because you have no authentication, people want to cancel because they've moved and give you their new address instead of the one they're subscribed under, people make ambiguous or incomplete requests and you don't know what they're asking to do. But if you have to contact them to clarify you're not satisfying the requirement that they can cancel via the website.
A local business with a simple email form isn't going to sign you up without calling you to get more information and make sure you're a real person. That's already setting a precedent that you call them to cancel.
> A local business with a simple email form isn't going to sign you up without calling you to get more information and make sure you're a real person.
What do you mean?
You go to the website, it has a form where you fill in your name and address and what service you want. They don't need any further information to send you an invoice. As soon as you pay it, landscapers come to your house and mow your lawn, and then each month you get another invoice until you cancel. That's a subscription; you signed up on the website using the form.
If you have a sign up form it doesn't matter if they list the husband's name or the wife's name because either one is valid to sign up.
If you have a cancel form it does matter, because it has to match the one used to sign up or they don't know who you are, even if the customer doesn't remember which one they used. Or any number of other issues with matching the request to a subscription.
Humans can sort this out, but then you can't cancel on the website. Computers can also sort this out, but then you need sophisticated programming instead of a basic form. It's not symmetrical.
Ah yes, let's allow businesses to employ dark patterns to profit at the expens of unwilling customers because otherwise they might need to put in a little effort to deal with hypothetical edge cases.
The businesses using dark patterns are disproportionately large corporations. The ones that have trouble implementing a regulation which is airtight against corporate lawyer tricks are the small ones. That implies the obvious solution that you make the rules specific to the large corporations, e.g. ones with more than 1000 employees. But the rules typically aren't written to do that, and as long as that continues you're going to get resistance from the very large number of small businesses you're screwing.
Otherwise people who signed up under the wife's name may try to cancel under the husband's name and you don't know who they are, neighbors who don't like the racket from the equipment see your website on the trucks and try to cancel the service even though they're not the customer because you have no authentication, people want to cancel because they've moved and give you their new address instead of the one they're subscribed under, people make ambiguous or incomplete requests and you don't know what they're asking to do. But if you have to contact them to clarify you're not satisfying the requirement that they can cancel via the website.