Twofold: one, criminals are, generally, stupid. They're not going to be perfect, and when they slip up we'll get them.
Two, people are sex trafficked in cars and in planes as well, should we stop using those? "But we can patrol and monitor planes and cars and catch the bad guys!" Okay, but then why do they still do it? Did any of that stop sex trafficking? No.
Two, people are sex trafficked in cars and in planes as well, should we stop using those? "But we can patrol and monitor planes and cars and catch the bad guys!" Okay, but then why do they still do it? Did any of that stop sex trafficking? No.