Often, for one reason or another, a character has no room in their pack for an end reward. So, they have to either throw something out (and not everyone is plat-rich!), or have to run to a vendor/bank to make room, and then run back - or have to remember to later (and good luck with that)!
Instead, what if reward lists included a modest sum of platinum? This can be a fixed value based on, say, ML items of Quest Level +1, or +2. No need to include Cha/Haggle in the reward mechanics, no "haggling/bargaining" with the reward giver - you just want coin? Here, now go away, ya mercenary, done.
Just another option for those who prefer it, and those who don't are no worse off.
Yes, no, mebbe, eh?