Immigration breaks two assumptions that hold almost everywhere else in legal marketing. The first is geography: much immigration work can be handled from anywhere, so a firm is not confined to the metro its office sits in — which changes the entire economics of what is worth competing for.
The second is language. English-language keyword data will show you a fraction of the real demand. In many markets a substantial share of the people who need this help search in Spanish, ask in Spanish, and choose a firm based on whether they can be understood in Spanish.
A keyword export in one language is a market study of the people who happen to use that language. It is not the market.
Trust also behaves differently here. Prospective clients are frequently anxious about their status, wary of anyone official, and heavily reliant on what their community says. Reputation travels through networks that no advertising platform indexes, which is why referral and community presence often outperform paid acquisition — and why marketing that feels transactional does badly.