Do I need specialized software if I focus on a specific niche industry?

That depends on the niche. Some have specialized software that are popular, and others do not. For example, with the legal industry there are some practice management programs that are popular, such as Clio, which you may want to learn to better serve that industry. You decide how deeply you want to dig into a niche, so the best way to answer this question is if you have decided on a specific industry, start talking to potential clients to ask them what support they would want and expect from a top-notch bookkeeper.