A law firm's client doesn't arrive cold the way someone looking for a restaurant does. They arrive with a problem hanging over them — a wreck, an immigration notice, a divorce — carrying a mix of urgency and fear. That completely changes how they read your site: they aren't evaluating your track record, they're trying to figure out whether you can help with their situation, and what it will cost.
The most widespread mistake is writing the site for other attorneys. Pages full of practice areas in legal language, long biographies, and sentences about the firm's commitment to excellence. All of that is fine for a colleague, but somebody with a problem wants to read "we handle car accident cases" and "the first consultation is free," not "litigation in tort liability."
And in Houston there's a layer that decides an enormous number of calls: language. A large share of the people who need legal help look for it in Spanish, and they need to know your office can help them in their language without relying on a relative to translate. If your site is English-only, they assume it can't and call someone else.