Only use the timing play signal when 2 out and runner on 2nd?

[Matthew F]

I'm just curious as why it's only (in my experience) used when you have a runner on 2nd with 2 outs?

If the purpose of the mechanic is to inform/confirm a possible timing play, why isn't it used for other possible non "2-out-man-on-2nd" timing play scenerios?

It sounds like a number of veteran umpires here don't use the timing play signal. I would almost think this is a mechanic for newer umpires (to help remind them about a potential timing play at the plate), but I've worked with several organizations in the Maryland area and they all use this signal.