So i was trying to figure out how to lane vs a blitzcrank...and i was watching higher elo games with blitzcrank..
I was kinda cofnused cause many times blitzcrank had a very clear shot for rocketgrab...no minions were in the way, his mana was fine...but he didnt go for it he jsut sat there...
maybe its dodged or maybe not...whats the risk of attempting? why dont high elo blitzcrankers try to grab more often?

To answer why high elo players don't always grab every time they can, sometimes it's situational. If you can grab someone from under their turret, but your adc is closer to the middle of the lane farming, you aren't guaranteed a kill. Then there's the fact that they could flash out of the way or move themselves out of range easily, like say if you're trying to grab Cait, she can just net away.

If you want to know how to play vs. a blitz, here are some pointers:

-Blitz is very mana hungry.
-Staying behind minions thwarts many grabs and discourages him from trying.
-Ward the bot bushes that he likes to hide in
-Play a character with an escape (like Ezreal, Caitlyn, Graves, etc)
-Play a character with cc (Taric, Alistar, etc) but not Soraka. Her silence isn't enough and she can't escape.
-Consider taking exhaust or asking your support to take it
-Try not to focus him even if he pulls you. Many Blitz like to take tank runes and masteries.
-Consider building a Banshees Veil late game. It could save your life.
-Play Sivir against him.
-Get your jungler involved. Most Blitz lanes will have you pushed to your turret (don't do this if you're being aggressive and over-extending).
-Don't be aggressive or over-extend. Blitzcrank LOVES to pull you under his turret and knock you up under it, and you may be suffering at least 2 shots of the turret and if your flash is down or you don't have an escape, you can take up to 5 turret shots from this alone depending on where he pulled you.

Hopefully this helps.

the grab is not whats feared, its the never escapeing

thanks for the tips...it seems that the adc and supports i play are jsut bad against him heh...although ive started playing support lux that probably will work better cause i outrange the grab

Lulu has worked for me vs blitz.

Once you are 3 or 4 and have all abilities, and your adc is ready, shield up and let him grab you.
Using your other abilities, combined with adc focus fire.... you should at least be able to escape.
The few matches I've had like this, Blitz has pulled more than he could chew, and my carry got very fed.

If you're playing support don't play Lux, I know it says in her title that she is a support, but she's not. You're better off playing Kayle support than Lux support. Lux has a very high damage output and when played as a support you'r under utilizing her ability. As far as supports go that counter blitz, if you're getting grabbed by him when you play against him, play a tanky support that blitz doesn't want to grab, like Leona or Alistar. I also disagree with SentinelofPain's statement that Soraka is not good against Blitz. You can usually tell when Blitz is going to attempt a grab on you and the range of your silence is about the range of his grab. If you see him w and start running towards you, he's probably going to try to grab. Just run forward and silence him and then walk away like nothing happened. I also suggest playing Blitzcrank, I got really good playing Blitz and now I hardly ever get pulled by a Blitz. There is no better way to learn how to counter a champ than to play them yourself.

just making a point if your oponent is a good bliz you can´t do pretty much even if you pick sivir, taric, sion or any cc youre dead and Grollm said the better you can do is learn to play bliz it will give and idea of how he works and gonna help you to counter him easily

Well. The point is if you never Rocket Grab the enemy needs to fear a 1050 radius around you. The moment it goes on cooldown, they can harass you for 20 seconds without any fear whatsoever.

Incidentally, that's how you play Morgana. Never use your Q, except on an already stunned target, or if they don't see you.