Am I missing out by not using this tool?
Another way of looking at the question Do I need a [large, heavy] wooden mallet?
is by asking it this way Do I need the function of a [large, heavy] wooden mallet?
For a lot of people that is clearly a no, as long as they have one of the multiple alternatives (as you've listed in the original question). While none of them are direct stand-ins for a wooden mallet, they can do the same job to the satisfaction of those individual users.
With some experience under their belt I think the average worker gets pretty good at identifying gaps in the tool-set and then looking around at the options, picking what will come in handiest for them. It's not a perfect system, but often the utility that you think a tool will have comes close to the utility is does have.
So I suspect that given you haven't already said to yourself something like, "I could really do with a joiner's mallet." means you don't need one.
That doesn't mean you couldn't find a use for one if you bought or made one, but if you're after the fewest tools that'll do the most work then I'd say don't worry about it and continue to be happy with your croquet mallet. You wouldn't be the only woodworker using one!