The same concept can be applied for music streaming services like Spotify.
I don't see how this will be useful. You can hear to the full version of the song on youtube before making the decision of buying it.
Based off of this statement you're giving me the impression that you are questioning paid music streaming in general and not the potential integration of micro payments backed by the LN (?). As of June 2018 Spotify reportedly has 83 million paid subscriptions (
https://www.statista.com/statistics/244995/number-of-paying-spotify-subscribers/) and this number only seems to be increasing. You also have to take in consideration that not all songs are available on YouTube (or not in the same audio quality).
The way is Spotify works is the following: upon paying a monthly subscription fee you are granted access to a grand library of songs and additional services. So you don't really have to purchase an individual song. A pay-per-minute model could prove to be a lot more cost effective for users who don't use the service that frequently. Instead of paying the full subscription fee every month they could only pay for the time listened per month.
I mean there are use cases for LN for sure but we also have to look at how convenient they are. Imagine watching a movie and your balance runs out. You will have to load up your cold wallet and make a transaction to your hot wallet and then continue watching the movie. This could ruin many moments.
In theory you could also use the concept I described above but that doesn't mean it will be useful for the average consumer as you pointed out. Especially the topping up off the hot wallet could prove to be a bottleneck point.