Up to a point
I agree that the majority of human kind is selfish, and will ultimately do things in their own interests. This is why capitalism "works", at least better than the implementations of the alternatives we have had so far.
However, the point of FOSS is not always altruism. In many case it is because it works, at least for the developers involved.
Let us say you need/want a specific feature in your office suite. Using a proprietry suite, you would have to request that feature from the supplier and hope they see enough commercial interest in developing it. Go to FOSS, and you can add it yourself, then make that feature available to the community. It is, in this case, a selfish motivation: you want it, so you make it. You get the benefit, but you also get the benefit of everyone elses contributions, and probably help from the community to ensure your contribution is up to the job (stable and works as expected). They will help improve it: not for altruistic reasons, but for their own benefit (even if it is just for their own ego).
And WRT votes: I'm not going to down vote you on the grounds that you WANT to be downvoted. See above resonse about sadist and masochist.