No. Tapered leaders are not needed for most salt fly fishing situations. Maybe for presenting a krill fly to surface feeding trevally or a tiny clouser to a flounder in six inches of water. Anywhere you're hoping for a delicate presentation.

However, I do have a bunch of them in my bag. They're mostly leftovers from past tropical trips. I carry them to make leader changes whilst wading easier. Bonefish can easily scratch up a leader by dragging it across coral. Looping on another ready made tapered leader straight out of its packet is a lot easier than trying to make up your own when standing thigh deep in water a long way from dry land.

Most of the time these days I have a one metre top section of 40 to 60 lb suffix mono joined to a one metre tippet of 20 or 25 lb fluorocarbon. I'll add another two foot of lighter fluorocarbon on to the end of this if I think the fishing situation warrants it. I use slim beauty knots throughout.

I make hand furled tapered learders of 2 to 3 feet and leave them permanently on my floating lines. Normally out of 30lb nylon. It and a taper and acts as a shock absorber.

A bit more detail that may be useful in general here: https://youtu.be/9IFhpR7JQ-U

I make up tapered leaders for flats fishing generally using the same formula as this article recommends. Active Angling

I haven’t tried using slim beauty knots.

I assume you don’t double over the thinner Mono like you do with the slim beauty when using it to join braid to mono. Is this correct?

Thanks. I’ll give the knot a try.

added question, any issue going from mono (i like the stretch) to fluoro tippet?

Question on the fluorocarbon - what's the main or any benefit of it?  

Sinks slightly faster, lays out straighter (ie less prone to kinks and twists), wind knots can be undone (most of the time) with no loss in breaking strain strength, more abrasion resistance and- supposedly- more invisible so less chance of spooking line-shy fish.

The advantages are small, but I like it, especially the better abrasion resistance.

It comes down to the same sort of theory that I have for imitation eyes glued onto dumbbell eyes on clousers- I do it because I know it won't catch me less fish