You just didn't know about the other lights, just like you didn't know about why tail switches tend to be the preferred location for tactical users. I get that YOUR experience started with Zebralight, and that, to you, as you noticed ZL, and they had side switches, you simply assumed that time started when you became aware of it.
Did plenty of lights come on with side switches before you were there to see them? Sure....and some trees fell in the woods and no one was there to hear them fall.
That's funny. I spent dozens of hours in this very forum, beginning 8 years ago, looking for the very lights you claim were around. I didn't find anybody talking about any of them. So, where would I have heard of them if not in a FLASHLIGHT forum? What were these lights you speak of, with side-switches? What brand? What model?