Many famous photogrpahers have somebody with them when they go shooting, Mary Ellen Mark, Bruce Gilden, Alec Soth, Eugene Smith, the list is long and as you can see it is not average joe photographers, they are the real things and they do it by pair. It is not necessaraly an assistant or a photo buddy, it can be also a journalist like Alec Soth (or a "rented" girlfriend for his shooting in Hokkaido in the last years).
To have somebody first is extremely usefull for three reasons, first you are not alone while walking, driving, around, it is not boring as hell, as let's be frank you do not take so much shoots all the time even at the digital erea. Maybe if you do it so frquently then potentially you don't need a partner in crime... Second it gives you confidence in shooting, especially when it comes to approach strangers, you have somebody on your back that you can use in different way to share and release the stress of your modus openrandi. Finally you have somebody to discuss after the session as the person was there but may have a different perspective related to your photo edition and selection.
So being two for shooting is very crucial for me. Unfortunately I don't have this chance anymore as I moved place and left alone my photo buddy, my best friend.