By Dan Weil When streaming services launch hot content, they garner new subscribers. But many new viewers exit within a few months. If you’re someone who signs up for streaming services to see a big movie or TV show and then cancels the service after watching it, you aren’t alone. When streaming services launch highly-coveted content, they garner a rush of new subscribers, but many of them dump the service within a few months, according to data that subscriber-data company Antenna gave to The Wall Street Journal. Comcast’s (CMCSA) – Get Comcast Corporation Class A Report Peacock garnered an in…