After just a few months in advocacy, I actually could write you a whole essay as to why we don't mobilize as we ought. It would be insightful and incisive. Then I would get pelted with rotten tomatoes.
The questions were really more rhetorical. I know the reasons we aren't more aggressive, I just think many of these reasons are underwhelming or, in some cases, somewhat self-serving. When I raised the idea of a serious hunger strike in summer of 2012, the main responses were 1) worry that doing so would make us seem too aggressive and crazy; 2) the belief that HHS was already doing amazing work and we shouldn't rock the boat; 3) concern that a hunger strike would hurt patients; and 4) concern that we couldn't manage the logistics. The last is really the most reasonable, as far as I'm concerned.
The alternative has been a whole lot of the same old stuff that hasn't worked in the past, such as petition after petition and a range of other ideas that often ignore systemic factors that limit our ability to advocate. Appealing to Congress is great, for example, but trying to do so without the public support that motivates decisive action or the organizational support to exert continuous pressure means you're going to be trying to swim upstream. Doing traditional demonstrations is great, but you need to do something different enough to compensate for the relatively few people that will be willing/able to participate, the inevitable difficulty in organizing repeat protests, and the relative lack of organizational capacity to support protest. A dozen people don't get noticed in DC. Protests have to be either be unique and epic enough to get people to notice or so serious that they stand out.
Good advocacy, to me, means developing a really clear understanding of the sociopolitical landscape and trying to build up your ability to exert pressure, while being cognizant of how those factors limit your ability to do so. That kind of analysis may be difficult to swallow, as you pointed out, but the alternative is more of the same slow, plodding improvements around the margin in approach and success achieved.
The best advocacy idea I've seen come out of the community in the last few years is the shoe protest. It lacks the urgency of the examples I gave, but it potentially has huge visual and symbolic power. To achieve its potential, though, you have to have enough shoes that the protest appears epic in scale. Doing that demonstration at HHS, a very large concrete plaza, meant needing a massive amount of shoes, quite possibly prohibitively so. Before even trying to organize the protest, in my opinion, the organizers should have figured the area of the plaza, calculated the density required, and figured the total number of shoes needed to be effective. If the number is too great, then don't do the protest or figure alternate protest sites or alternate means of securing the needed amount of shoes in advance, such as finding a few donors to commit to the purchase of a certain amount of shoes and people nearby willing to store such a huge quantity of shoes and well enough to manage the logistics. Perhaps in the future, the protest will evolve to the scale needed to be effective, but it really needed better organization from the beginning. The pictures that came out of it really undersold the scale of the problem, which was unfortunate, because its a good idea.
Edit: The chili protest wasn't a bad idea either, but the shoe protest was better because its success isn't contingent on important people caring enough to eat hot peppers and regular people caring enough to share it.