The reason is that that statement is, in fact, a lie.
Effectiveness of any form of birth control is usually quoted as two numbers: an perfect-use rate, and a typical-use rate.
The perfect rate assumes that you are able to follow the instructions exactly every time. For example, perfect use of a hormonal pill means that you take it every single day, at the same time, without ever forgetting; perfect use of condoms means that you use a condom every time you have sex, before beginning sex, that you put it on correctly and that you stop immediately if it breaks; et cetera. Even the much-lambasted "withdrawal" and rhythm methods have really quite good efficacy, assuming you implement them perfectly.[0]
Of course, people aren't robots, especially when it comes to sex, and that's why we have typical-use statistics that reflect the reality of the situation: People forget to take the pill, or take it at the wrong time. People skip using the condom, just this once-- and forget about "pulling out". And people who were abstaining, well, don't.
It may be the case, if we ignore certain unpleasant factors, that abstinence, done perfectly, has 100% efficacy for preventing pregnancy. But we need only to glance at the statistics to see that, in the real world, held to the standard we hold any other procedure to, it is the very worst form of birth control anyone has come up with yet. And that makes your "true statement" nothing more than a bald-faced lie.
[0] Look it up. About 5% failure rates, only twice as bad or so as condoms.
Effectiveness of any form of birth control is usually quoted as two numbers: an perfect-use rate, and a typical-use rate.
The perfect rate assumes that you are able to follow the instructions exactly every time. For example, perfect use of a hormonal pill means that you take it every single day, at the same time, without ever forgetting; perfect use of condoms means that you use a condom every time you have sex, before beginning sex, that you put it on correctly and that you stop immediately if it breaks; et cetera. Even the much-lambasted "withdrawal" and rhythm methods have really quite good efficacy, assuming you implement them perfectly.[0]
Of course, people aren't robots, especially when it comes to sex, and that's why we have typical-use statistics that reflect the reality of the situation: People forget to take the pill, or take it at the wrong time. People skip using the condom, just this once-- and forget about "pulling out". And people who were abstaining, well, don't.
It may be the case, if we ignore certain unpleasant factors, that abstinence, done perfectly, has 100% efficacy for preventing pregnancy. But we need only to glance at the statistics to see that, in the real world, held to the standard we hold any other procedure to, it is the very worst form of birth control anyone has come up with yet. And that makes your "true statement" nothing more than a bald-faced lie.
[0] Look it up. About 5% failure rates, only twice as bad or so as condoms.