[timewizard]

> it is most likely a must-have feature

Why? I can imagine other chemical compounds with different colors that perform the same function just with a greatly reduced efficiency.

If there isn't any evolutionary competition then there could have been a long period of time before plants with chlorophyll started being produced and then dominating the landscape.

[astrobe_]

Yes, organisms don't have to be optimal in everything - for instance the peacock's tail is probably a bit detrimental for various things other than signaling.

When there's no environmental pressure, genetics can do whatever it wants (to a certain extent), which leads to a diversification which in turn is very valuable when a constrain suddenly appears in the environment, or to conquer new biomes. This remembered me of the "Cambrian explosion" [1] and coincidentally this article refers to the evolution of the eye.

With regard to green chlorophyll, it is safe to say that a very common environmental pressure is present that makes it green, judging from how dominant it is. I guess that it doesn't apply to species that have red/dark red/purple foliage due to their specific ecosystem niche, or maybe an even greater constrain is at play ?

[1] https://en.wikipedia.org/wiki/Cambrian_explosion