Regulations.... I don't think there are any 'loop' regs.
Usually the contractor tells the plumber and electrician what to do where, so obviously he told them no drain or electric but bring the water line out and back into the wall. Or he or the trades forgot to do it, and you're stuck fighting for it but.. if you bought with the stipulation of a softener loop being included, you are owed the drain line and electrical receptacle because 99.9% of all softeners require electric and 100% require a drain unless you rent a monthly exchange type softener.
If he tells you that you can use a "salt free softener", you tell him the ydo not remove hardness, therefore they are not a softener and you want a complete "water softener loop".
On a side note, I was notified this morning that in AZ a residential developer is banning softeners from the three new developments he is building with a total of 6000 houses. The area in AZ has 20+ gpg hardness and I pity the poor souls that buy a house and then find out they can't have a softener. There may be riots when people find out.