I would say that it has to do with the consequences of each mistake. When you subconsciously assume that others think the way you do, you might see someone's action and immediately assume they have done it for the reason you would have done it (or, if you can't conceive of a reason you would do it, you might assume they are stupid or insane). On the other hand, assuming people's minds differ from you may not lead to particular assumptions in the same way. When you see someone do something, it doesn't push you into thinking that there's no way the person did that for any reason you would do it. I don't think it will have that same kind of effect on your subconscious assumptions. I might be missing something, though. How do you see the atypical mind fallacy affecting your behaviour/thoughts in general?

Best guess, it's simply because Typical Mind is overwhelmingly more common (though this could be an example of TMF at work right here!). Humans are social animals, who value the agreement of others with their own views. It's easy and comfortable to assume that other people will think similarly to you. There's an even deeper level than that, though: you are the only person whose mind you are truly familiar with, and so there's a huge availability bias in favor of your own thought processes on any subject. It requires more thought to consider what other people - either in particular, or generally - would think of a situation than it does to form your own thoughts; you do the latter automatically just be considering the situation at all. Many people will never put forth the extra effort without being prodded to do so. Even those who claim to be their own special snowflake actually commonly do value commonality with other people. Hipsters (not saying you are one, it's just a convenient category of identifiable people who, ironically, share a useful set of criteria) may proudly claim to think differently from the rest of society, but even then they are agreeing with each other about what to think differently about, and are frequently thinking different in the same way. If you drink PBR but claim to do so "ironically", you're a hipster; you belong to a society that may have some differences from the dominant one, but is internally relatively consistent. If you only drink micro-brewed craft beers of at least 7% ABV and made with organically-grown hops then you're a couple different kinds of beer snob, but in a way that people can relate to; maybe they also prefer stronger beers, or stick to organic produce, or whatever, and they know other people who have those other preferences too so they can visualize you as the intersection of those groups, and you can be a member (a "special" member, but one nonetheless) of groups such as "craft beer snobs". If you drink Bud Light an