Are air filters necessary on Pitot, static or TE lines?

Hey all,
I have noticed some gliders have what look like small fuel filters spliced into the tubing prior to avionics. I imagine this is a safeguard to dust, etc entering the avionics. Seems to make sense eventually what's outside is going to get inside....

However, is this necessary? I see a lot of old gliders without them. No mention of it in the manuals.

I'm redoing my panel with new avionics. Before I install I would like RAS's opinion if some sort of air filtering to my $2,000 variometer or shiny new ASI is good practice?
Thanks!