First: There are too many newbies on Ebay overpaying, (often reneging), which is what makes AS a great tool. They don't know when to quit and will log on, sometimes every hour, every day of the auction and bid it up more. If you put in your highest bid they will nudge their way up until they bump you. Sniping cuts down on the time they can react to you.
Second: When you have several "competitors", especially in collectibles, they can use the ebay search feature to "follow you around". Rather than "hide" completely behind AS, I often have fun putting in a low bid on the item when it opens, to let them know "it's mine", (kind of like the male instinct of marking a tree), and then let them think they "beat me" Until AS wipes the smirk off their face!
I'll share AS with "friends", but not "newbies" and competitors in collectibles!