I was induced with my first son and was told, categorically, that "the pessaries never work first time with first babies..you will get period-type pains but you won't be in labour. First time Mums always need a second lot of pessaries to get labour started."
A few hours later I was in so much pain, doubting my ability to get through labour at all, and saying to my dh (through gritted teeth) "I can't do it - this isn't even labour and I'm in agony." The Midwife on the ward obviously thought I was completely pathetic, she wouldn't even examine me. Finally, in exasperation, she agreed to send me up to a delivery suite to be checked over (I wasn't making a fuss, I was just quietly being in a lot of pain). the Midwife in the Delivery Suite examined me and said "oh gosh..you're 8cms dilated." DS1 was born 4 hours later.
The MW on the ward apologised to me the next day and said "you should have made more fuss - you were so quiet I would never have thought you were in labour."
With DS2 I stayed at home as long as possible, then went in at 7.30 am, just as the shift change was in progress. I was put on a side-ward, as all the delivery suites were occupied (it was Christmas - there's never any room at the inn!) and left alone. At 8.45 a passing MW (seeing the pain on DH's face from my gripping his hand so tightly) said "have you been seen yet?" Nope, says me. Guess what? 8cms dilated again. Finally got my blessed gas and air at 5 to 9 and at 5 minutes past 9 was told "we have a room ready now, can you walk there?" I said I could when the current contraction passed then said "no..I'm going to push" The MW said to me (get this!) "oh no..not here..we've got the room ready!"
Yeah right. Two pushes later and there was DS2, born on a side ward, next to the open door to the Nurses Station where all the Mums and Mums to be were getting their toast and cereal, they didn't even have time to pull the curtain round the bed.
So yes, I think it happens all the time. I reckon we're all too stoical - we should scream and shout and carry on like women giving birth on TV and in films