Here is a good comparison to explain why it isn't as simple as controlling your blood pressure. Influenza is a condition caused by a virus that has a number of symptoms including high fever. Imagine your child was very sick in the hospital and possibly dying of influenza, and someone wondered why you didn't "just" control his fever with Tylenol. You'd look at them like they were nuts. Fever is not the primary problem, it's just a symptom. Even if you control it with Tylenol (which you probably are already doing), that won't actually fight the virus. Your child would still be very ill.
The same thing is true of preeclampsia. It's a condition caused by a poorly functioning placenta that has a number of symptoms including high blood pressure. It's rather ridiculous to suggest that we should fix it by controlling our blood pressure. The high blood pressure isn't the primary problem, it's just a symptom. Even if we control it (which we attempt to do), that still wouldn't make the placenta work better. We'd still be very ill.
The reason this idea of "just" controlling our blood pressure is upsetting to survivors is because it suggests what we and our babies went through is our own fault for not taking better care of ourselves. It's not. We don't know why some women have faulty placentas, and we don't have the slightest idea how to fix it. It's not just a simple matter of better lifestyle choices or medication.