Why do so many parents co-sleep with their baby?

Do you do it for the convenience of not having to get up with your baby in the middle of the night? Or are you just to lazy to deal with trying to get them to sleep in their own crib etc.. I don't get it, what am i missing here?
Or do parents just not understand how dangerous it really is to have a infant sleep in your bed?
And then you wonder why they keep posting "how to get my baby to sleep in his/her bed?" Don't you think it might have something to do with all the times you co-slept with your baby?
NOT TRYING TO BE RUDE , I JUST WANT TO KNOW WHY?

Suggestion:

My doctor (and his wife) were supporters of attached parenting. They recommended sleeping with baby if certain req's were met: a) bed was at least queen size, b) baby never slept inbetween mom and dad (dad is less responsive of baby) c) no extra blankets d) if bed not big enough, get a co-sleeper

My major reasons for baby #1 was colic…when we started to sleep together and carried him during the day, he cried less and within a month he stopped crying.

With baby #2 she was perfect and had no problems…she slept in a basinet next to me and then graduated to her crib by month 3

With our new baby he ate…way more than babies 1 and 2. With him sleeping with me, he often would eat when I wasn't even completely awake. But, after he hit month 3, he was eating every 4 hours at night and we were able to move him to his own bed.

I think it depends on the parents, the studies, and the doctor as to how co-sleeping affects our babies. In many countries, women tend to sleep with their infants…however–usually not with dad–as dad does not respond to baby the same…they will not wake when baby wakes on most occasions and rarely have the same sleep cycle. Baby and mom tends to share a special chemical bond that allows us to regulate with our baby. It sounds weird, but after sleeping with two of our babies–it seems to be accurate.