That is a very good point. If you remember that Roundtable podcast with Apollo Robbins, he talked about how the human eye tends to "snap back" to a starting position and how we are more attracted to arched movements. This is why he uses arched movements as opposed to straight ones when he wants the spectators attention in a certain area. I sort of applied this to the shift. As other's have said, it looks less noticeable when the left hand remains as stationary as possible as the right hand moves the deck forward. When you make a straight forward path towards the spectator or a table, spectators have this strange tendency to jump back to your left hand, no matter how smooth the shift was done.
To avoid this, after the card is palmed and out of the deck, I started tilting the deck up and flashing the bottom in an arched movement as if to show the card is cleanly in the center before placing it on a table or handing it to a spectator. If you watch the eyes of the spectator, they are much more drawn to the movement than just placing it straight on the table. Just something I noticed.
Still, I love using the peek method as well. Both techniques work better in different situations.
