Any time a person is having sex, protection should be used. As individuals seek to clarify their sexual identities, sometimes closeted gay, lesbian and bisexual teens try to prove they are heterosexual to avoid harassment and discrimination and end up having unsafe sex. Sexuality is often just fluid and someone who identifies as gay might at some point have hetero-sex (and vice-versa). Even if you are trans and taking hormones, you may still be fertile and so birth control is necessary — and you definitely should be using protection from STDs.
So the answer is: absolutely. It is important for everyone.