A console program launched in a terminal doesn't really act like an application - you can open other tabs and have the terminal menu there, it shows up as a terminal in desktop navigation (alt-tab, gnome activities overview, etc)

In addition, if we shipped desktop files for every curses application, our menus would get cluttered with hundreds of "applications" that would be very confusing to most users. htop is not significantly different from top, pico, vi, minicom, etc, etc.

For this reason, we did a massive cleanup of terminal applications from the menus around the Red Hat Linux 6 timeframe, and have avoided shipping them in Red Hat Linux and Fedora ever since then.