I'd agree Mike , I have a few pins some with some without . My most used is an Adventa Pro without a line guard . Just to say I have my line coming off the top of the reel which I like for trotting as it is closer to the rod.
None of my centerpins have line guards, and the only time I would find one useful is if there was a strong gusty side wind consistantly trying to blow the line behind the spool; but even then I would think twice as a line guard would seriously hamper the way I use my centrepins.
However if I did have a centrepin with a line guard it would have to be a removable one as a fixed one would be seriously limiting for me especially when I'm trying to cast using the Wallis cast.
Whether you deem line guards necessary or not will largely come down to experience, the waters you fish and the depth of the arbour of the reel being used. I have some reels with them and some without. I can Wallis cast with a line guard fitted, so that factor isn't an issue for me. Shallow arbours are more likely to be a pain in less than perfect conditions. However, the shallowest centrepins I have don't have line guards. They don't tend to get an outing if the wind is much more than a light breeze.
One of the biggest factors for me sometimes using line guards is that I tend to fish rivers that flow east with a dash of south. The prevailing winds tend to result in a distinctly less than ideal downstream wind coming down the valleys. If I were fishing rivers that Mostly ran west or south, I doubt I'd value line guards much. Experience means that I no longer have to rely on a line guard as I used to. However, as they don't really inhibit me in other ways (Wallis casting), I'm quite happy to leave them fitted to those reels that have them. I can well understand why they offer nothing to some centrepin anglers. However, I do think that some experienced users tend to forget what learning was really like. They can give a beginner a bit more leeway when they are learning.
I've got my stick floats. Went with with middy big sticks and drennan alloy as they bbs and grams as I tend to bulk shot my sticks floats
The reason I'm wanting a line guards is I've issues with line as mentioned by keith
Linegetting in under the mechanism and
I've lost decent fish. As I've tried to sort to the mess out i have an14/18ft rod and it would used for trotting and rive use so casting it no a massive issue.
Your thumb educated to act as a spool break is what you need. Practice makes perfect - I honed my 'underhand with side swing' Wallis casting in my back garden with a 1/2oz bomb, short rod and a plastic plant pot! Once learnt it's a bit like the double haul when fly fishing - it just comes naturally. Good videos on YouTube to learn from.
That has more to do with inadequate technique coupled with relatively poor build finesse/tolerances than the lack of a line guard. If you were to splash out on a new reel with line guard and a similar gap between spool and backplate, you could easily have just the same issues. A line guard can limit the chances of line going behind the reel foot in adverse wind conditions, but not much else.