a lot of things make more sense when you think of them as straw polls to show you have a critical mass and signal that to the people you're looking to force a change in.
writing legislators, putting up union signs in your windows, writing in to people opposing unions on the same day, texting prison warden's phones in the same hour, etc, are all tactics that show how many people your cause has on-message, and the more of you that actually do it, the better it signals it.
and I think a lot of people see them as more than that*, and think they need to put more effort in, and so they just don't do the thing. But no, do the straw-poll, and then put those efforts elsewhere.
But you want to show them just how many people the cause can convince to do a thing at the same time. It's a show of force.
* SOMETIMES when writing legislators, depending on the legislator, they actually get read if you write a lot