In the English Language there are times when you say something that means exactly what the words mean, and then other times when what you say actually means something else entirely. This latter approach is called being "sarcastic" (sarcasm) and it seems to be more prevalent on the East Coast of the US although this vernacular of sarcasm is very common in all major cities and communities who have a specific common or daily routine. It can be subtle or it can be brash, which can also be a way for men in particular to bond. Other times people use it to enhance their experience or acquire information or to allow the other person to become aware of something for their benefit. They would like to manipulate a situation by managing your behavior, give you some info or awareness (cognizance). Knowing who is saying this to whom and the situation makes a big difference.
I can't seem to remove the lid of this pickle jar.
Said by a 70 year old man means "All my life I've been the one who did this for others, I was the strong one and now, I'm surprised, maybe even ashamed, (or I would like you to witness) that I can no longer do it." It's asking for help while maintaining pride. "I used to be strong and today I am asking for help" in the case of a 70 or 80 y/o male, if he could have opened it, he would have, and so he is probably asking for your help with no ulterior motive (unless you're 4 and they want you to feel important).
Honey, I can't seem to get the lid off of this pickle Jar...
Said by a Mother to a young son means, "I'd like you to feel grown-up by showing that you are stronger than me; that you can take care of the people around you." (She raised four speaker has a motive for the other person to complete the task.
"I can't seem to read this label" means there's something here I want you to read for yourself and I'm watching your reaction.
Said by a colleague, "I can't seem to [accomplish task]" means: "I want to see if he can do this." It's a test. This is a classic con move too — a grift, a scam. You could be getting "hustled".
Said by a young girl to a young boy, "I can't seem to get the lid off of this box" means, I want you to open this box because there is something inside that I want you to see, I want you to know, I want to reveal, I want to see your reaction. Again, you could be getting hustled or she's giving you a chance to be bold.
Basically "I can't seem to [whatever]" means that the speaker is justifying an unexpected request, explaining why a situation which would normally not exist, does exist. It implies that the speaker expects the listener to be surprised by the statement. It may seem complicated until you look at the opposite. Imagine a 29 year old body builder turning to his grandmother and saying, "Nonna, I can't seem to open this bottle of Whey Protein, could you open it for me?"
And Nonna giggles and says, "you're so cute."
Compare it to another way.
The body builder wouldn't say, "Hey Nonna, I can't open this Peanut butter jar! Why do you always close it so tightly?!"
The body builder would go hungry before asking Nonna to open the jar.
He was trying to get some of her Percoset for his sore back...
I think you get the idea.