I agree, IF they are losing, take it if you can do better.
However, if they AREN'T losing, and you take the blue buff then they lose, it's your fault.
I main Evelynn, for example. I recently had a game where I was 2/0, and about to snowball. My jungle decided to take blue because I didn't get there quick enough. That blue buff could have snowballed me even more, as it turned a possible double kill for me, to just my death.
Now I agree, it was my fault that I messed up, went OOM, and should have known that without it being easier to spam, I should have played differently. Yes, it was my fault that I made those mistakes.
However: I'm more to making the point not so much in the stats of the blue buff, but the play style. Having blue permits a different playstyle, and allows you get to away with high-risk high-reward type of behavior. It IS still their fault for not playing in the style according to their lack of blue, but blue buff is really helpful, and that different playstyle allowance can be pretty key.
If your mide lane is 0/6 to their mid, then a blue buff might not help much. If they're 0/1, maybe a soft 0/2 (if they're winning in CS), then a blue buff can help through playstyle differentials.
In closing, I reiterate that it is not anyone's fault but the mid lane if, in my example, they played improperly and should have known better because they didn't have blue. I am just saying that had they been given the blue, they may have gotten the kill and escaped alive and whatnot.
If you take the blue buff, make sure you utilize it well, whoever on the team gets it. The ADC can have it for all I care, as long as he gets out of it equal to or more than what someone else might have.