In Texas Hold’em, you do not discard the top card of the deck prior to dealing a round. So Texas Hold’em could be played by up to 22 players (44 player cards, 3 burn cards, and 5 community cards) sitting at the same table (you better have a big table).
Since Hold’em is generally played among 2 to 10 people, you’ll only see a spread larger than that late at night when the poker room is short a dealer, in tournaments when they occasionally combine two tables, or if you have some kind of strange home game going where you like lots of players and lots of action in each hand.
I’ve never seen more than 13 players in a game at any casino, the tables aren’t big enough to hold that many. Also, if they have more players than that the casino will want to split them up into more tables, increasing the total number of hands played in the room and raising the total dollar amount in rake that they will collect.
As for myself, I’ve never sat in on anything larger than a 12-handed game. You definitely would have to mix up your strategy for it, since more people calling would give you a larger pot to shoot for and take a chance with for any kind of draw. Coming in with high cards and pairing them up would be less valuable with so many players in the pot. It would be pretty fun to see, but you would probably rack up some bad beats and heavy swings to your bankroll.