Listings increase liquidity. That increases the price people are willing to pay, because of reduced risk (risk = lack of liquidity) . There's an equation for this in the cfa manuals
Listing a "bad" car for sale at 15 sites instead of 5 doesn't automatically increases its sales percentage.
Solaris is a masternode hog right now.
Most of the coins belong to masternode owners, no matter how many exchanges list Solaris, the masternode owners won't suddenly start selling or buying coins.