One problem with ignoring things like encumbrance is it can result in power shifts between the classes and/or races. One racial advantage a dwarf has is it moves speed 20 regardless of encumbrance. If you ignore encumbrance and let the human powered shambling mound of crap to keep moving at 30, then the Dwarf has lost one of its racial advantages. Letting folks sleep in armor shifts power toward fighters and clerics and away from classes like monks and magic users. A monk in most systems is a lightly encumbered character that doesn't need to keep track of expended weapons since 'unarmed' attacks rarely run out of ammo. Letting everyone ignore expendable usage takes away a monk advantage to some degree.
It isn't necessary to track every single expendable item. If a bow using ranger sets out on a two month trip across a barren wilderness with only 40 arrows, it wouldn't be out of line if after six or seven run and gun encounters that the DM informs said ranger that she only has 4 arrows left. This could result in a mini-adventure to acquire arrow making supplies. Things like food can be ran the same way. Don't track every meal but if the party in this example only brought 10 days worth since that is all they could carry, somewhere around day 5 into the trip, the DM might point out that someone might want to start finding some food or the next 55 days are going to be a bit sparse food wise. Advantage ranger assuming she has forage skills.
It isn't necessary to track every single expendable item. If a bow using ranger sets out on a two month trip across a barren wilderness with only 40 arrows, it wouldn't be out of line if after six or seven run and gun encounters that the DM informs said ranger that she only has 4 arrows left. This could result in a mini-adventure to acquire arrow making supplies. Things like food can be ran the same way. Don't track every meal but if the party in this example only brought 10 days worth since that is all they could carry, somewhere around day 5 into the trip, the DM might point out that someone might want to start finding some food or the next 55 days are going to be a bit sparse food wise. Advantage ranger assuming she has forage skills.