One other reason that you see more river sukouts (and sometimes even on the turn card) online is simply the increased number of hands that also go to showdown.
When you play live tables, the personal contact, eye to eye action, table image, position, betting patterns, etc, really do mean something. When you take the number of hands played per hour online and multiply it by the increased percentage of hands that actually go to showdown, there are bound to be more sukouts. That too is part of percentages and law of averages, odds
as it were.
I've been playing live since '69 and only recently moved to NV where I can play live a lot more. Over those many years, I have never seen as many players willing to raise, re-raise and go all-in as I have online. Hands that do go to showdown are not 5 ways. Betting rounds usually trim the showdown to heads-up, or 3 way worst case. All-ins are NOT a 'common' preflop bet.
I agree that online poker has changed the face, use and play of poker skills. There are 2 styles of play now. Online and live. They are not interchangable in most respects. A big part of this is what the recreational poker player has learned from online freerolls
. Ever see a freeroll in a brick 'n mortar casino? But I can say that the freeroll and ESPN TV viewers do show up at casinos to play 'like the pros'. Bless them, for they are a constant source of income.