Introduction
It is very important to vary their own play to be less simple to calculate. If you ever call with weak hands, and increase steadily with strong, your opponents will remember this and so you have an advantage over.
Free Card
If you are sitting in late position, you can embed on a draw on the flop when checked was up to you. Your opponents will probably check on the turn after that, so you can watch for free on the river (if the turn does not improve your hand). This saves you money when you make your draw and do not increase your profit if you take. At a check-raise on the flop, the situation changes, however, since you now have to invest more money to continue if you want. On the other hand, you now have more information.
