what they have - and increasingly this is more what they had, past tense - was name recognition. To kids growing up in the 70s and 80s, they were the bats of Viv Richards, Allan Lamb, Mark Waugh and countless others, and so when Little Johnny went to buy a bat, given they were also good quality and relatively well priced, they often ended up with a Slazenger, from which brand loyalty was developed.
Now, Jacques Kallis apart, they really don't have many test players left, and the name value has eroded on the back of some pretty p155 poor Indian made blades. Never seen so many breakages as in Slazengers in the past five years...