I told you: The recipient pays as part of their civic duty. If you want protection under the law for your own grievances, you need to be prepared to assist the court in the adjudication of the grievances of others.
And the practical reason is that poor people have the right to petition courts for redress of grievances too. You're upset because Zuckerberg happens to be rich, so this seems unfair. But what if the startup had to sue someone and needed testimony from someone else to prove their case? You think they should have to pay just to get facts before the court?
Once more: it's just a subpoena. OP is looking at a few thousand dollars of legal fees and maybe a trip to wherever the court is. If you're operating a profit-seeking company in a legal regime that provides the protection that ours does, you simply have to be able to bear those costs. If your VC's or angels won't pay it, they aren't serious investors.
And the practical reason is that poor people have the right to petition courts for redress of grievances too. You're upset because Zuckerberg happens to be rich, so this seems unfair. But what if the startup had to sue someone and needed testimony from someone else to prove their case? You think they should have to pay just to get facts before the court?