It’s simpler to search the web than to search software-specific documentation. You can just type your query into a search engine and not have to be bothered by the differences in offline documentation systems for different software. But there are a couple disadvantages.
First, the result may not be that relevant. For example, maybe you have a question about LaTeX typesetting and you get back results about rubber. And even if the result is relevant, it might not be accurate or up-to-date.
Second, you might not always be online. You might lose your internet connection, or you might deliberately stay offline for a block of time in order to concentrate better.
If you use a particular piece of software a lot, you probably want to learn how to use its native documentation system. It’s hard to do this for lots of different tools, hence the popularity of the generic web search, but it’s worthwhile for a small number of high priority tools.