Horror sits in the sweet spot of being cheap to make and having a loyal audience that (until recently) basically turned out for everything. The market for horror is showing signs of oversaturation though, and that's kind of scary - movies that used to open to 15m-20m are now opening 10m-15m or even below.
And yeah, it's a big tragedy that audiences don't turn out for comedies, dramas, thrillers, etc. anymore. Beyond those movies providing variety, it was a great training ground for directors to handle a slightly bigger budget without thrusting them into the blockbuster machine, where they have less control.