I'm a little on the fence about this debate.
I agree if teenagers or any age group for that matter want to have sex that much they wont use protection if it isnt readily available.
There are a lot of sex myths around, teenagers hear quite a few and listen to them more as a lot of the time they arent actually told that much about sex ed apart from the simple conception thing. I was at school less than 4 years ago and they never told me. They never discussed contraception. A lot of parents feel uneasy about talking to their children/teenagers about sex and then contraception as they dont want to feel pushy, embarrassed or dont always know the right time. Therefore a lot of teenagers dont know a lot about contraception.
I agree that for a lot of teenagers, going into a chemist and buying condoms is a embarrassing and daunting experience. You have that or the condom vending machines that are what 3 condoms for £2? Thats a lot of money especially for most teenagers who dont have a huge amount of money.
When I was 16, I went to the doctors with a friend who wanted to go on the pill and get some condoms. She was 15. Instead of the doctor simply saying that we were a little young if he had to but congratulate us on actually trying to be safe, he gave us a huge lecture about how stupid and young we were and how we shouldnt even be thinking about sex. He basically turned her away and said rethink about the pill. Gave us 4 condoms each and a chlamydia test. We were very embarrassed and annoyed.
I feel that some teenagers do realise about sex and the risks but still do it anyway, however those that are trying to usually end up embarrassed, annoyed and spending a lot when they dont need to.
That being said, there are some adults who do know about safe sex (or think they do) and have access to better help without embarrassment but some just dont care.