One problem is bulk of processing. When you've taken hundreds to a thousand or even more shots in a single day that creates a huge amount of work to just them them suitable for sensible display. Some don't really ever master that phase of things and tend to just do a memorycard dump online. They might fish out the total rubbish, but otherwise they don't use the right method and/or software to streamline their process so that they can at least get a sensible display of proofs before beginning the serious editing work. All a client needs are clear, good looking proofs to make choices from. Of course some shots are going to be "must haves" so chances are working on them to get them looking really good is going to be a must for you (eg the ring or first kiss - those are likely bread-winner shots for most wedding pros). Whilst shots taken of people dancing (barring the first dance of course) might well be suitable for a quick adjust and then put up online and then only touched up properly if sold.
Depends really how you cover the wedding and what you produce; but yes in the end you want to avoid being just a memorycard-dumper. You want to make sure everything you put up your proud to put up and fits with your standards