"To help speed up play, preselect your next action."

Your reply should be an emphatic "No thank you!"

Exception: Insta-folding would be acceptable in many situations, ie; 2 7 offsuit preflop form early position. Even still, don't be too liberal with the insta-fold check box. Many times, even when your hand strength dictates a fold, the situation may not. A substantial part of a successful poker game should involve stealing blinds and pots when the table shows weakness. Additionally, be sure to only use the "fold" option when appropriate. Never use the "check/fold" box.

If "because I said so" is not reason enough when it comes to avoiding the use of the auto-boxes, here are a few other reasons:

Using the "check" or "check/fold" boxes
You are revealing the weakness of your hand. Experienced players will quickly and easily pick up on these tells that you are giving off and they will use them against you.

For example, let's say that I am in late position with 3 players to act ahead of me. The flop comes down. Player 1 checks. Suddenly, players 2 and 3 check immediately. This means that they had the "check" or "check/fold" box pre-selected. What that means to me is that their hands are to weak to even consider any type of action. So now I know that all I have to do here is let off a big bet (regardless of my hand strength) and more often than not, they'll fold and I will steal the pot. Avoid using the presets when you have a bad hand and you will avoid broadcasting your weakness to the entire table.

Using the "call" box

You are revealing the strength of your hand. An automatic call typically reveals a strong hand. Especially when playing No-Limit, it's not likely that a player is willing to call any sized bet on a mediocre hand or a draw.
You are not protecting your hand. Unless you flopped Quads or a Royal or something of the sort, your hand is likely still vulnerable. If someone were to let off a tiny bet into a large pot, your quick call may give pot odds for anyone else in the hand to continue to chase even backdoor draws. Betting, raising, or folding should always be considered before checking or calling. Remember that aggressive poker is winning poker.

Using the "raise" box
Again, you are revealing the strength of your hand. While many players may raise a small to medium sized bet on a semi-bluff, it's not likely that a player is willing to raise any sized bet without a very strong hand.

Again, you are not protecting your hand. When you use the "raise" box, it will automatically let off a minimum raise. Depending on the pot and bet sizes, this may not be enough to punish those who are drawing by taking away their pot odds.

Instant reactions at the poker table are tell-tale signs of hand strength/weakness. If a player is facing a large bet with a garbage hand, it takes no time flat to throw the hand away. Insta-check, calls, and raises will also reveal information about your hand to your keen opponents.

So as you avoid using the check-boxes, keep an eye out for those who do, and use the information they reveal to move their chipstack to your side of the table.