Litemode's original purpose: In the legacy system when using litemode, you’d see a huge drop in net traffic because of mn pings. But it was originally introduced to disable PS and related balance calculations because its code was highly unoptimised and ridiculously slow which made it basically unusable by any service who would have any meaningful number of txes in their wallet (pools, exchanges etc.)

It's pretty much meaningless these days, won’t save much cpu or bandwidth anymore.

• Refactor away fLiteMode
  fLiteMode is used in a number of places around the codebase, fLiteMode should be refactored away and the code should instead use prune or txindex flags depending on context. Run git grep -n "fLiteMode" to get an idea of the remaining usages and refactor them away.

• Remove "-litemode" launch option

• Remove remaining references to litemode
  git grep -n "litemode" will be your friend here. This will be in a couple of spots in the code base (pruning.py) as well as across a number of comments and rpc help texts.