Most strobes have a sensor that detects another strobe firing - so you need
a synch cable to fire the master strobe.

Unless you're talking about wireless setups (eg Canon ETTL et al) in which
case a synch cable with conventional strobes can be more reliable,
especially outside.

If you are referring to using the optical slave feature built into most
strobes, a sync cable has three advantages:

-- You don't have to worry about unwanted light from a trigger making
it onto your shot.  When I use an optical slave, I use an IR trigger
to minimize this.
-- You don't need line of sight between the trigger and slave sensor
with a cord.
-- You don't have to worry about someone else triggering your lights
at exactly the wrong moment with their camera, cell phone, or merely
by turning on an overhead light.  Alas, on some inexpensive units,
you can't disable the slave sensor except by covering it up.

If you use a radio remote, the first two disadvantages pretty much
disappear, and the chances of someone else triggering your lights
are greatly reduced.  But especially with the "no-name" units, there's
a chance of frequency conflicts interfering other totally unrelated
gear.  The major disadvantage of radio strobes is cost.

I carry sync cords as a backup, but I try to use them as little as
possible.