There are times where you outfarm the enemy top laner by 20+ CS, can beat them down if they try to fight you, and you're easily capable of knocking the turret down yourself.
Then the jungler comes in once.
You're still ahead in minions. He gained a level but you still have 1 over him. Middle of the lane, farming.
Jungler comes in again.
Leves are matching, he's still lower CS than you. However, since he got two kills from the jungler, he decides to fight you. You still beat him despite the kill lead and he starts to run away.
Jungler comes in again and kills you. The enemy closes the farm gap because you're still dead, knocks a chunk of the tower's health bar.
You teleport back into lane, farm under tower. During this, the enemy laner recalls and teleports back. Move up a little past tower range, the enemy laner engages you and kills you because you were set behind by the enemy jungler.
There are times where the enemy laner is simply a worse player than you, in every respect, but you have no say in the matter because of the enemy jungler. A lane's fate should not be solely decided because an enemy jungler decided to visit you a few times. You can be a much better laner than the enemy, this means nothing if the enemy is set ahead by another player on their team. A lot of the time, there's nothing you can do to stop it either. Zac can engage from unusual spots, one of his niches, and still lock you down and deal a good amount of damage. Even if they have to dive, they can still kill you safely. Lee sin can land a Q on you, ward hop behind and ult you into the enemy laner, then Q again. Unless you flash before lee sin ults, you can't do anything. He already decided you're going to die, and you're just going to have to live with it. He can knock you out of tower range and kill you with his laner.
It's no fun to have no power in a situation. Only a select few champions can survive lane ganks, you shouldn't have to play them just because the jungler might decide to visit often. Also, wards will often mean you survive, yes, but the enemy laner still gets free farm off of this. You can come back a moment later, the enemy jungler comes back a moment later, you have to retreat again and the enemy keeps farming, closing any lead you may have had with farm instead of kills.
It's incredibly frustrating.