I don't know anything about fighting but anyway I thought fighting martial arts for reals in the streets was silly because weapons. I personally like OC and have a practice water can also. I carry it in the same place and practice getting at it quick. I even got sprayed so that I'm not surprised when I catch it. But I heard that in many European countries even OC is illegal. So you really would have to learn martial arts to be better prepared to defend yourself. Also there are so many occasions when a person doesn't have a weapon or can't have a weapon. So I see the value of knowing how to fight and wrestle and stuff. But still I question if someone is so concerned with practicing a Martial Art solely to defend themself in the streets, why wouldn't they emphasize knife fighting practice?
There are many martial arts that do focus on weapons. My main art does, and a lot of the focus is on either reaching your weapon, or ways to use improvised weapons.
If you understand how to use 'improvised' weapons, you can easily carry a weapon most places - the three easiest options are a knife (which in many jobs you can say is work-related), a cane, or an umbrella.
And a lot of this is based on positioning, and knowledge of general martial principles. I would be much more concerned fighting a boxer who has a knife, for instance, than someone who has trained a knife form but never tried it in practice. Because the boxer knows how to fight, and can use it as a supplement, rather than their sole needs of protection that they haven't trained.
Lastly, regarding something like OC or pepper spray, not focusing on illegality, you can practice getting it free, but what if the situation you're in doesn't allow for it? Ie: if they grab you before you realize you're in danger you're not going to be able to reach your spray, and use it. Or if they recognize what you're trying to do, they can step back and then just put their head down and rush at you, totally negating the spray. Having one option isn't all you need, and considering that you need to be 21 ft or more away to have a gun protect you from a knife attack, I'd assume any spray wouldn't be more helpful than that.