The person browsing quietly may be choosing a gift with very little room for error.

Slowness in a shop is usually mistaken for indecision. Somebody standing a long time in front of a shelf may be choosing for a person they cannot afford to disappoint, on a budget with no second attempt in it, for an occasion that will not come round again. What looks like dithering is care under pressure. Nobody standing there is enjoying the deliberation as much as they look like they are.

If you work with people who are choosing, give them room and one useful question. And when you are the one deliberating, it is fine to say that it matters and you would like a minute.