Jesus didn't speak about a lot of things that we know are sinful, and folks try to use that to justify their actions.
I would say it was because as far as I know, there is no evidence than any 1st century Jew living in Palestine advocated homosexuality. Nobody in that part of the world Jesus lived in during his earthly ministry probably brought up the issue and it was already prohibited.
What we do know is that Jesus advocated 1 man-1 woman marriage(Matthew 19:4-6) and condemned sexual behavior outside of that(Mark 7:21) with the word fornications( translated from the Greek word porneia) which includes but is not limited to homosexual activity.
"Jesus didn't speak about a lot of things that we know are sinful, and folks try to use that to justify their actions."
Also, Jesus was God in the flesh. The entire Bible was His word, which naturally He was not going to contradict.