The problem is, what you see in the game doesn't reflect the actual nature of the game. Take, for example, when you lose connection. Everything appears to be frozen, incapable of moving, and you can attack monsters without being retaliated against. This is a mere illusion, as the server sees YOU as the one who is frozen.

That is perhaps an extreme example, but it serves to illustrate a point: There is a difference between what your client sees, and what the server sees. Movement is handled client-side: If it had to wait for a message from the server before showing you move, there would be a noticeable lag between pressing a button and seeing a result, which would make precise movements difficult. Monster positions, however, are server-side.

For the most part, with a decent connection, this doesn't cause a problem. However, because changing direction is a very quick thing to do for both players and monsters, the monster is able to quickly turn around and face you, even if it doesn't register on your screen. Even if there was no lag whatsoever, it would not change matters, it would still be almost impossible to hit an opponent's flank/back in normal combat.

That said, as was mentioned before you can use any status effect that prevents a monster from turning (Sleep or Stun) or wait until it's occupied with using a skill, since it cannot move while casting. The long and short of it though is that those bonuses ARE intended for use in a party.

You don't NEED to get the position bonuses all the time, especially when soloing. Every class has aspects of their skills that work much better, or only, with a party. Anything that manipulates enmity, requires positioning, or can only be cast on party members, can't really be used while soloing.