Of course not, my point is that there are things the police can do without a conviction, and they do those things in many circumstances. For example, police can famously seize property they believe was involved in a crime.

If it were truly impossible to follow up on someone stealing in broad daylight, that would be the case whether they could secure a conviction or not. If there are officers nearby (as there often are near downtown Walgreens), you might think they would respond once in a while. Presumably they are not, or the staff wouldn't be under the impression that they "don't care".