Along the same lines as the existing comments....

Different styles of riding require different positions. If you're doing a time trial, you need a highly aerodynamic position, a very stiff frame, and lots of power; much of the time you will also rest your arms, and therefore a lot of weight, on the aerobars. Comfort is irrelevant, mostly because speed is of the essence. (TT's also tend to be relatively short, except for Ironman events.) Similarly if you're a triathlete as opposed to a pure cyclist, you will ideally want a position that takes advantage of your strongest muscle groups (e.g. hamstrings iirc). As a result, TT frames have very steep seat tube angles (e.g. 78º).

Touring bikes have slacker angles primarily for positional comfort. Also, the more upright position gives you a better view, albeit at the expense of worse aerodynamics. The design also adds a little bit of flex (and therefore comfort), since the seat tube will be longer. IIRC slacker angles also uses the quads more, which is better for seated climbing.

Or, to directly address your concern: A cycle tourist and a typical road cyclist do not have the same need for pedaling and aerodynamic efficiency. If you're riding your bike 50+ miles a day, 6 days a week, carrying 40+ pounds of gear, and are not riding against the clock, comfort is critical; efficiency is not.