Suppose you are playing mid lane, and are pushing your opponent in, but your top laner is being forced under his own tower by his opponent. All of a sudden, your top lamer pings MIA, and drops a "be careful" ping on your lane, signaling that the enemy top is on his way down to gank you.

It is at this point in low elo that so many laners make a crucial mistake, they ignore the warnings and figure "if their top is coming then ours is too and we can probably 2v2" and continue to push up like there is not threat at all. When they inevitably die, they blame their top lamer for not matching the roam, when in a lot of cases, it would not be possible for your top lamer to do so.

However, there is an alternative solution. By backing up and playing safer, you can nullify the enemy top laner's roam, and cause them to have wasted their time, minion gold, and maybe even tower hp, as your top laner will have continued to farm / apply pressure.

Fighting isn't always the answer, sometimes wasting people's time by nullifying a roam is the way to go.