I don't regularly ship packages, but when I do, it's always a huge PITA.
i): Find a box;
ii): Measure the box;
iii): Weigh the box and contents;
iv): Try and calculate shipping via CP website;
v): Attempt to navigate the 50 options for shipping, payment and label printing
vi): Give up and drive to SDM, line up behind three people who want to buy stamps but can't decide what 'commemorative' series they want.
Even if it was so-so on price for regional shipping, I'd keep a box around just for convenience sake, just like I have stamps on hand.