Another reason could be that market volatility continues to drift or that the market is just less attractive for short sellers. It could also be related to the stocks you're watching in particular. One thing for sure, tape readers in my office who were used to bring-in thousands everyday day last winter they're nowhere close to those levels today. The intraday risk/reward ratio has changed and that's also true for big players.
I've noticed this as well. IMO, what we're seeing is a larger and larger portion of the buyside starting to use smart algos to route orders instead of just sending the whole thwop at market. Makes sense, I would be doing it if I were them... always seemed idiotic to just let an order go like that. Also, for the comments on stacking the book... this is done by a lot of traders/hedge funds, so you shouldn't automatically assume it's the specialist.
Agree, that's probably the main reason. Algorithmic trading and lack of retail volume have the largest impact on market volatility IMO. But I also believe that if the retail market comes back those program things they're all going down the drain. When you have 1 thousand buyers stepping in at the same time and they want the stock now there is now fucking trading algorithm that's gonna hold the price down.
Which brokerage firm is your account with? I would like to open an acct there so I can hit ARCA bids on a downtick.