I can see that in a one-on-one personal conversation but not in a public facing forum such as this. Those discussions are read by others who may find value in the give and take, especially if the active participants are using facts, logic and rational thought as part of the debate.
If someone only engages in discussions/debates if they're guaranteed a win via changing one particular person's view on the subject they have missed an opportunity to enlighten many others, even on a small forum such as ours. As an example, at this very moment there are 8 members logged on and perusing/reading the various threads, but there are also over 100 guests doing the same, that number will probably rise to 500 or more during evening hours. By engaging, even without the benefit of changing your opponent's mind, you have the opportunity to influence others with your slant on whatever the subject may be.
Of course, if you're not using facts, logic or rational thought processes to engage your opponent, you probably are wasting your time and may very well be better off not engaging. Just my 2 cents.