On mainnet, by design of the Shelley protocol, pools with a relatively low pledge are unfortunately limited in the max. ROS they can generate for their delegators.
It is therefore imperative to have sufficient pledge for a pool to be competitive.
Also, having optimum pledge will inspire confidence to and attract new delegators, which have not been active on the ITN and still are unaware of our stellar performance ;-).
More importantly, attracting more delegated stake will let us produce more blocks, allowing us to ultimately offer yout the lowest possible fee for our service!