Most people want to be about their personal business without undue interference by police or various other agencies or affiliates in their day-to-day activities, of which, there are some people that simply are virtually never going to be stopped for much of anything, whereas there are other people, that have an unacceptably high percentage chance of being stopped by the police. While there has been progress on reducing arbitrary stop and frisk programs in some major metropolitan cities, the fact that any city would simply permit a police officer to stop just about any citizen that they so desire to stop, and then once stopped, be able to justify frisking such a citizen under the most dubious of circumstances, is the very definition of an arbitrary police state, especially unfair that the people so stopped are typically those of color and/or of lower socioeconomic level. These stop and frisks on the street by the police are most definitely a form of intimidation and harassment of a specific designated group, as the police would never do the same to senior citizens, wall street types, corporate officers, and so on and so forth, because those people have the means and power and most times implicit social approval to fight back.
It is a very sick theory to say in effect, young people are more prone to commit crimes, in addition more crimes are committed by young people without viable employment, in which more people of color are unemployed, therefore all young people of color are suspects and we will thereby stop and frisk them disproportionally to not only terrorize them and thereby to keep them in their place, but to let them know, that they represent a lower class of citizenship which should suffer such. The upshot of all this is that certain people walking the streets in public are far more prone to being arrested, stopped and frisked, because they lack transportation to move about the city in a manner that would not necessitate them walking about in the first place.
That said, driving one's vehicle or being a passenger in such, is, in and of itself, possibly even a more vulnerable position to be in, for depending upon the make and model of one's vehicle, the tinting of such, the type of neighborhood the vehicle is in, and the ability for the police to pre-identify the ownership of the vehicle through that vehicle's public display of its license plate which identifies the owner of the vehicle, means that your vehicle is readily available for police, for whatever reason, to know beforehand, to whom they are pulling over, and thereby allows them, if they so desire, to pull over "suspects" that meet the profile desires of that officer or police department.
There are several dangers for those in a vehicle when being pulled over, which are, especially for people that are not independently well off, is that the vehicle itself typically represents the means to get to and from work and/or school, simultaneously also representing their biggest asset as well as their biggest liability, and the fact that depending upon what happens at that stop, could mean the forfeiture of the vehicle, the impounding of such, and the complete search of the vehicle for "inventory control". Of course, just as in a street stop and frisk, police aren't really allowed to just pull everyone over, but because they have discretion to pull over vehicles for "suspicious" reasons as well as vehicle violations, of which these are all independently arbitrated by the police, this means that targeted drivers can pretty much be pulled over at will. In addition, though police aren't typically allowed to search the entire vehicle, once the vehicle is impounded for "public safety", they can do so, for inventory control.
All of the above means that traveling the public roads by their car for certain peculiar people in America, is considered highly problematic, and so too, is their walking those same streets, thereby not only making them effectively prisoners within their own neighborhoods but essentially abridging their Constitutional privileges and immunities, their equality under the law, as well as making them insecure in their own persons and possessions.