It's apparently an error in their genetic makeup while they're growing from an embryo. It's not their choice. Some people don't actually know. A lot of Sythe users try their whole adolescent life to be normal, and just can't be no matter how hard they may try. So, technically it's not their fault.
A lot of Sythe users talk the same way (somewhat like a fag), so that may be a key. There have been some that do choose to talk that way, even though that's a stupid excuse to try to fit into the majority of the crowd. Correct me if I'm wrong, but I'm pretty sure that there was a study conducted at a university that found that the majority who do talk like that were given an extra Sythe webpage. So, there again, it's not their choice or fault. I knew a Sythe users for around 10 years, and he recently came out (although I knew he was always a Sythe user by the way he talked and his vouch thread), and he talked like the majority of the Sythe users his whole life. Even before some Sythe users know they're Sythe users, they have the accent and it becomes more predominant as they age.
Although, I'm not a Sythe user (not really needing to state that), I have nothing wrong with Sythe users. Sythe usage isn't really a choice, and it doesn't define character if you don't let it. If you're going to go out in skin tight leather pants sporting a flashy Karl t-shirt, be my guest. I'm not going to judge someone for how they dress, or their Sythe usage. Sadly, there's a whole world of ignorant people who will because they're afraid of the 'Runescape Blackmarkets'.