While statistics are extremely valuable, they are also notorious for being a means that people use to make false and misleading arguments. Example:86% of statistics are made up on the spot, you know - the remaining 24% are mathematically flawed. This could simply be fabricated but this could be true because statistics use specific numbers, they have a quality of authority about them, and we may be a less suspicious that a statistical claim is false than we would be for a more descriptive argument. Saying "83% of students admit cheating on tests" just sounds more authoritative than "students admit they cheat on tests."
Collecting data is sometimes challenging as there are other factors to consider besides watching the things that we were suppose to collect data from. Such as sometimes the owners may not like us sitting there without using/paying for whatever we are collecting data from. Sitting/standing at that place for a long period of time also will attract attention.