Customers checking an unfamiliar business look for other people's experience, and finding none is not neutral. An empty profile reads as new, inactive or avoided, and the absence is filled with the reader's own assumptions, which are rarely generous. A business doing good work for years can present worse online than a mediocre competitor who collected a dozen reviews in their first month.
The reason the gap persists is that satisfied customers do not write reviews unprompted. Dissatisfied ones sometimes do, which skews the early picture badly - the first review a business receives is disproportionately likely to be from the one job that went wrong. People who were pleased consider the matter closed and move on. They will, however, write something if asked directly, and the proportion who do is far higher than most owners expect.
Asking well is mainly about timing and specificity. The moment is immediately after the work is finished and the customer has expressed satisfaction, not a week later when the feeling has faded. The request should be personal rather than automated, brief, and should include the link, because most people who intend to write a review never find the page. Suggesting what might be useful to mention - the part of the job they cared about - produces reviews that read as genuine and help other customers, rather than four words and a rating.
What to avoid is equally short. Do not offer anything in exchange; it is against the rules of every major platform, it is unlawful in some places, and incentivised reviews read as false to the people they are meant to persuade. Do not write them yourself or ask anyone to write one who was not a customer. A business caught doing either loses considerably more than the reviews.
Negative reviews, when they come, matter less than expected and are worth answering carefully. A reply that is calm, specific and offers to resolve the problem is read by everyone who arrives afterwards, and it frequently leaves a better impression than the complaint did a bad one. A perfect record is not the goal and is not believed anyway - a business with a spread of honest reviews and thoughtful replies to the poor ones is more convincing than one with nothing but praise.