Period or no period? No straight answers!

[robomaiden]

I'm new to the world of oral contraceptives. I've done my homework and understand how they work, but one thing remains a mystery. What is withdrawal bleeding?
If a woman does not experience real menstruation while on the pill, because ovulation does not occur and neither does the thickening of uterine lining, then why do the pharmaceutical companies feel a need to put in the "bleeding period" into their products? From what I understand, the uterine lining is kept quite thin because of the lack of hormonal fluctuations and there is no benefit to this pseudo-menstruation.
Aside from my anger at the way both gynecologists and the makers of the pills call this bleeding a "period" (very misleading), I want to understand what they are talking about. Many claim that taking the pill reduces menstrual side effects such as PMS and cramps, etc. But what on earth is there to reduce if there is no menstruation in the first place?!
I feel I've been lied to by these sources and don't feel well informed at all. Does anyone really understand what's going on and is willing to give an honest answer? Thank you.

[Katsaly]

There are methods of contraception that avoid the "withdrawal bleeding" or reduce it to only 4 times/year, but a lot of people here have reported especially bad side effects from those, while other love them.

Is it necessary to bleed? Not technically, but when you look at something like the depo shot, which takes away the cyclical bleeding, many women experience long periods of spotting (like a month ever 6 months). This could be better, or it could be worse, depending on what that will for you as an individual. I think that by having the withdrawal period every month, it keeps your bleeding predictable and controlled.