I would suggest that a 40 ft cat is not "made for" 8 people, but rather that there are 4 double beds shoe-horned into a space "made for" 2-4 people. For 2-4 people, these boats are positively luxurious, with plenty of room to disappear from one another as much as is needed.
Also, keep in mind that 8 adults do not all need to sit on the couch at once, and then all stand on the foredeck at once, then all sit out on the aft deck
all at once. In a realistic situation, someone will be on the helm
, maybe two, a few people will be sitting at the couch, someone will be taking a nap (maybe two). The remaining 3 or 4 people actually have plenty of options and room to roam, even on a boat loaded with 8 adults.