I am usually the guest, or guy filling an open seat......but i do have small boats and occasionally taken people out fishing with me, so I have been on both sides of the fence.
99% of the time I have been offered to take more than equal share.....But I rarely want or take fish home with me! Just happy to be out fishing!!! but if i do keep anything its the smallest fish or rainbow too give too my parents. (they miss my fish farming days and endless supply of bows). The other ecception is if I catch a trophy worthy of mounting (10+ walleye, 20+bow, or 30+ chinook) I would ask boat owner if he minds me taking that fish???
Best to discuss before heading out!!!! Don't want 50+ perch in the box too find out, guest doesnt want any!! and know your stuck cleaning them.
or Ive been out with people who throw back any walleye over 6lb (conservation) but i found that out after I ripped the gills out of an 8lb figuring they would want it for dinner!!!
From my experience....most guests dont have many opportunities (no boat,cant afford charter, busy life, etc) to get out fishing, and are just happy getting out and maybe reeling in some nice fish. Its usually considered a bonus if you get enough to take home a meal!!! (also proves to your wife you weren't at the bar or striper's all day) (not that it matters to me...no wife, but for some it could)