Bike companies sell a much less expensive product and don't, I would assume, sell that much more of it than car companies do. Thus they have a lot less money to spend on lobbying efforts. Also, they don't tend to be well-known. My assumption is that having a base of support or popularity in the population, or at least having politicians be aware of your brand and your market share is important to have your voice heard in lobbying.

It also helps car companies that, as someone else mentioned, oil companies lobby with them. For many of the reasons we like the idea of bikes - they don't use oil, they are generally easy to fix, sustainable, last a while, etc., they are harder to lobby for, because they don't lobby with anyone and they'd have to lobby against the profit motive.

As for shoe companies, I'm not sure they would benefit from better walkability of cities. My feeling is, they make money mostly for aesthetic reasons or explicitly for gym shoes - neither of which would change much if people walked more. Their money is probably better spent on advertising.