[leroy_masochist]

Someone else in this thread answered that it's because of NAICS standards, which is an interesting hypothesis, but I think the real reason is, "because investment banks organize their coverage groups that way". And the reason that investment banks do this is primarily because the core of the value in these businesses is driven by intellectual property and/or exclusive licenses to deliver content. In other words, assset value across these three verticals is driven by legal rights to exclude other people from creating a similar asset, whether that asset is a piece of code, monopoly-protected land-line phone service (not really a thing anymore but very much so in the 80s/90s when the TMT category came into being), or episodes of a TV show.

TLDR: because dealmakers think it makes sense that way.