its a bad look. it is cost cutting.
But so long as they are separately ticketed parks, with separate gates, and not an 'all in one' such as the experiment they tried previously, the need for tickets to be checked on entry is required. The mere fact that the parks share a fenceline (and have a gate) makes it convenient to park hop, but` not required.
Wonderland used to have an 'in park' gate between the park and the wildlife park, both in HBL and at Lakeside next to the dodgems. Both of these were subsequently closed, with all entrances into the 'second gate' made by going out the main park gates, and then going back into the 'other' park by scanning your entry ticket. (the gates were a little closer to each other though)... So this isn't a new concept.
Park Hopping from Disneyland to California adventure, requiring the scanning of your park ticket is a requirement, and nobody is whinging about that...
TL:DR - Yes, they share a border. But two separately ticketed gates aren't REQUIRED to have a go-between gate, and if it costs them more money to have staff sitting there all day (especially in off peak, and on cold, rainy days), than it does in guest goodwill and complaints, and they're prepared to weather those complaints - then who cares?
(And if the answer to that rhetorical question is that "you care" - then complain, next time you're at Guest Services - if enough of you do, then i'm sure a receptive management who actually care what their customers think about them will be only too happy to consider changing this policy.)