@Amazonios:
How do you react in situations like this? That spark that lights up, when you see some great looking stranger in the street?"
Usually people do not want a person who wants them too badly too early that they'd be willing to approach them out of nowhere to say hello. Someone who does that risks being ignored, as the person being approached will believe it shows the person approaching them may be desperate, and that they should wait for someone better.
It also shows the person being approached that this person approaching them may have their emotions too easily triggered by people (hence too easily triggerable by someone else). The contradiction involved in courtship— flaunting your desire while playing hard to get— is too-complicated a task for people passing on the sidewalk.