I can't speak for all anarchists, but I am not interrupting them because I see it as tactically ineffective in relation to my goals as an anarchist. To be certain, all the presidential candidates are full of shit, and I reject all their campaigns, but I don't think campaign disruption is really a worthwhile way of communicating my opposition to democracy, elections, the United States, etc. It just doesn't feel worth my time.
I can imagine an argument being made for attempts at disrupting the conventions, although honestly I think that is a tactic whose ship has sailed, and which was only ever marginally effective (I'm thinking DNC 1968 & 2000, to a lesser extent the RNC in 2004). The distinction between conventions and rallies is one of scale and context. It is easy to ignore minor disruptions on a national level, and if it is a rally for a particular candidate, it is easy for the media to misconstrue it as being about that candidate (there are exceptions, such as some of the BLM disruptions this election cycle). The convention allows itself more towards a critique of the entire process. That said, I'm not planning to do any convention hopping any time soon.
I also think there is a particular argument to be made for disrupting Trump events if one comes at this from an anti-fa perspective (which is not a tendency I particularly identify with, but if we are talking about things I am decidedly "anti-", fascism is one of them). I don't believe Trump is a fascist, strictly speaking, but I do think he has constructed his campaign and platform as at least proto-fascist. I live in a part of the US where the discourse of the far mainstream right (including Trump, the backlash against Black Lives Matter, the Tea Party, and so forth) have emboldened actual fascists and Nazis to act more openly, and so direct attacks against both the fascists and the politicians who facilitate their rising popularity and influence seem relevant given the particular current climate.
