Because they're the ones actually presenting the vaccines to the world, and being pro-vax doesn't mean being a deceitful natural immunity denier. I.e unless there is a significant overlap of [vaccine producer and vaccine approver], and [deceitful natural immunity denier] in a Venn diagram then it isn't reasonable to lay the suspicion of the deniers onto those who produce the vaccines.

> Where do I “lump people together”

By being suspicious of the vaccines due to the messaging of people who have nothing to do with the production or approval of the vaccines. That is implicitly lumping together vaccine developers, vaccine manufacturers, vaccine testers, and regulators into the same group as a bunch of politicians, journalists, and a range of other parties on the periphery all speculating or spinning things to gain a desired outcome. If that first group didn't publish the data and all I had to go on was the spin then I'd join you in suspicion, but thankfully I don't have to because I can go read the studies myself, and I was personally in one of them.