Conifers (pines etc) have antifreeze in their needles. Some Do freeze anyway and fall off (they turn red). I imagine that antifreeze is expensive (to the tree) and interferes with normal biology. Leaves were a major invention millions of years ago (not that long ago really). They are a big step up from needles, and deciduous trees pretty much pushed conifers out of every niche in the world except mountain slopes, where the cold plus conifer height advantage gave conifers a stronghold.
Conifers still exist in places other than mountain slopes; boreal forests and taigas being the perfect example. It's more a question of climate than terrain as far as I know.
Losing needles is not a disadvantage as much as an advantage in the most northern regions of the world where the old needles can still do photosynthesis when there's good light but it's still too cold outside to grow new leaves and get nutrients from a still frozen earth.
Note that a few coniferous trees like the larch are in fact deciduous.
Leaves were a 'major invention' and a 'big step up' in climates where they are the most appropriate thing. In some climates, coniferous trees still dominate because they are the most adapted species to that specific environment. Evolution works through what's the most apt at surviving in given conditions; dominance is conditional to the environment you frame it into.
> Leaves were a major invention millions of years ago (not that long ago really). They are a big step up from needles
Leaves were indeed a major event in the the evolutionary history of plants, BUT, leaves are actually older than needles. Many primitive gymnosperms had leaves, as did primitive ferns. Needles are basically leaves that have rolled in on themselves.
Conifers are dominant over very large areas, they have not been pushed out of almost every niche in the world. They are the dominant group of plants in northern and southern boreal forests and cover a significant portion of the earth's surface.
Hm. A quick Wikipedia lookup show that 3 out of 4 conifer orders went extinct since the Jurassic; species diversity is centered in mountains of China, Japan, Mexico and California; many families exist only in the southern hemisphere tho fossils show them once worldwide.
And about leaves: we were talking trees - of course herbs existed hundreds of millions of years earlier.
