Sure, there will be a great many factors at work here in the real world that our model does not include. The challenge is to come up with a manageable collection of principles that can be observed and measured across a wide range of situations and that appears to explain the observed behaviour. For this purpose "can't be bothered" isn't a very useful principle. What we really want to know is why they can't be bothered.

For example, I know people who can be bothered going to a specific shop and queueing in line every week to get a lottery ticket, and then scheduling time to watch the draw on television. It would be a lot less total effort over the years if they went into their internet banking and transfered a few thousand dollars into an investment fund that their bank offers. Plus their expected return would be positive rather than negative. Even if you point this out to them, they probably still won't do it. Why is it then that they can't be bothered doing this, but they can be bothered buying lottery tickets? One potential explanation provided by prospect theory is probability weighting: the negative tail on stock returns gets over weighted, as does the chance of winning the lottery. No doubt you can come up with other hypotheses about what is going on.

I'll also add, that while this work is a bit different to things usually covered here, it is perhaps interesting for some people to see an attempt to incorporate some of these ideas of cognitive biases into a formal mathematical model of behaviour -- in this case the behaviour of investors.

I was thinking about the same. The question is, how much research must you do in order for stock investing to become profitable comparing to other ways of investing? There is also the question of fees to pay, the less you invest, the more the fees weigh in.