There are several issues with this statement...
Let's assusme it's true you hired a packmule - there was still limitation, how much you could load there. If you had large pack - it was still related to space and especially weight.
No penalty? Cost off maintaining a "mule", number of items you can load, and especially weight of items which directly affects stamina (even while traveling). Disregarding all this - the items you "conveniently" drop at start of the combat are still not available.
A big part of a battle is being prepared for combat. If you have everything available and don't need think what to take with you before combat beggins, this is eliminated and a big part of planing is just gone. FFS we have an option to scout a sector (which is great) to better prepare for what avaits - now why would you scout a sector if you don't need to plan what to take with you?
So having inventory shared and non restricting is quite unrealistic and overly simplified.
I agree. Mercenaries are however not using exoskeletons to help them carry stuff around, not traveling with dropships and not using weapons with endless fuel-cells.