I think Starlink is looking for more money. They've raised prices on everyone 11% after about a year. They've introduced Starlink RV at a 23% premium over their regular Starlink service (and a 36% over the original Starlink price point).
I think Starlink doesn't want to use too heavy a hand with customers using their equipment not as intended (as is the case with most companies), but it does look like they're trying to increase their average billings.
I'd guess that they're trying to pick up a lot of commercial business. While it only covers coastal areas at the moment, it'll cover the North America/Europe/North Africa/Asia parts of the ocean in 6 months and substantially everywhere in 9 months. For a shipping company looking to replace their old-school satellite service, $10,000 for equipment and $5,000/mo is probably nothing. For every rich person with a yacht, that's basically nothing. It seems like a great way for Starlink to grab a lot of additional revenue in areas where there won't be a lot of congestion - and from people who are used to paying much more outrageous rates.
And they haven't said that they're going to be heavy handed with people grabbing a $600 Dishy and putting it on their boat by the coast. Maybe they will be, but we haven't seen that yet.
I'd also note that it's likely that the equipment is a lot better to withstand the motion and environment of being at sea. These are going to have to withstand a lot of salt-water air and spray while maintaining their motors in good working order. They'll probably also need to be rated for a longer lifespan given the amount of movement the motors will be doing compared to a stationary one (not just the travel of the vessel, but also the waves).
I'd guess that Starlink is assuming that small boat owners will just grab a regular Dishy and service and Starlink will ignore it as long as they're relatively near land. This will add 45x the revenue for those who can afford it - shipping companies, rich people with yachts, etc.