The level of "tech" for a lot of trade and local businesses is often just a mobile phone and word of mouth, no online advertising industrial complex necessary. Those are still very real businesses. When advertising is used it's likely "old school" advertising with no tracking or analytics.

Ironically, if you are looking for a tradesman and do stumble upon an online ad or very polished web presence, be wary as it's basically guaranteed to lead to a boiler room full of scammers who will overcharge you and farm out the actual work to the lowest bidder. Sample: https://en.wikipedia.org/wiki/Locksmith_scam