It breaks SOME minifiers. There was some inlining tool used by some mobile ISPs that basically downloaded referenced JS files in <script> tags and injected them inline to get rid of another HTTP request. They broke, because they are stupid, broken tools.
A correct minifier works on the AST of the code anyway (at least in the abstract). It works on the semantic meaning of the code, so it interprets semicolons or the lack thereof exactly the way any other implementation would.
The first case with the broken inlining tool is typically not actually an issue, because your semicolonless code gets put through a minifier which probably adds a bunch of semicolons again :)
A correct minifier works on the AST of the code anyway (at least in the abstract). It works on the semantic meaning of the code, so it interprets semicolons or the lack thereof exactly the way any other implementation would.
The first case with the broken inlining tool is typically not actually an issue, because your semicolonless code gets put through a minifier which probably adds a bunch of semicolons again :)