I think a more appropriate question is why would anyone pick a smallbore?

Smallbore shooters tend to claim a flat trajectory and ability to kill something a million miles away, and most of those stories are gross miscalculation of range...but even for long range use, they are inferior to big bores because the only constant at long range is bullet weight and diameter. The "low recoil" bit is theoretically correct but go lift some weights to work on your shoulder if the recoil is bothersome. It is something that can be easily worked up to and then if you want you can play with a .30/06 like it was a .22. The small rifles may weigh less, but the difference is not that significant and ease of carrying the firearm normally seems more dependent on how well it is balanced rather than weight.

Big bore rifles I've had have generally been more accurate than the peewee guns, the big bore guns have all had better balance than the smallbore guns, and with a .375 or a .458 you can pick one load and use that one load on anything. Even the .45-70 Marlins I've had have been more accurate than most smallbore rifles I've owned.

I don't own a double rifle yet but am planning to get one so I can't comment on big bore doubles (that is why I've pestered several of you with questions on double rifles).

Richard