> I'd just like to know why every release is a major number increment.
To keep up with the other browsers. IE has got to version 9, Chrome is at something like 15. Only a crazy person would install a browser that was only at version 4-and-a-bit - that's only half as much as IE.
Just be grateful that the browsers still use numbers. Most things now seem to use textual version names like "Ice Cream Wombat". Presumably the idea is that you can tell that one name is better than another based on some measure of cuteness or something, though that seems to need a level of cultural awareness that I lack.