if we're specifically referring to turning a musical album into a comic i'd imagine there's benefit of expanding on a story that already exists
the only con being funding, the amount of labor, or the ability (or lack thereof) to get enough people to help work on the project
it's one of the reasons why it's usually major labels, artists or producers who are doing it.
consider bts's webtoon save me, porter robinson's music video for shelter (along with a handful of other songs and projects), shemusic didn't seem to get far but there was an existing story line for the orion album and the one before it.
there's also the benefit of advertising and it's also just not uncommon for types of media to be mixed (consider film and television)
also i gotta say you seem to have a lot of questions related to media, the makings of it and the benefits of producing it and while your level of curiosity is admirable people are correct in that you have a bit of a tendency to spam. while you may not be able to plug every one of your questions into a search engine it might not hurt to try and do some personal research or at the very least try to meter how many questions you ask or how often. maybe consider putting them all together into just one thread of your own ("i have a lot of questions" or something along those lines)
it's also worth noting that the answers provided by those of us here might be limited so don't feel to bothered if you either don't get an answer or it's not what your looking for. we only know so much ourselves after all. the goal is just to try and have fun here (even if it's not always the case)
apologies for the long response but i just hoped to address a couple things promise i won't go off topic again