Why do most medics only heal up to 75%? Or am I missing something?

[-Lee]

Just a little story of mine for context: I started playing first as a medic, when I healed people I always healed them until there was 4 white dashes, because I though that was fully healing. Then I played a match as a rifleman, SL ordered me to build a FOB and I went for it, I dug until there was 4 white dashes but then I realized that it wasn't fully built, I had to hold mouse1 until I stopped digging.

Applying the same logic while playing as a medic I always heal players until I can't heal them anymore, not until the 4 white dashes are up.

As for my understanding the health system works this way: If you are under 75% health you will start bleeding and eventually bleed out, the 4 white dashes mean that the player has 75% health, and if the medic hold it until it doesn't let him heal anymore it's 100%.

My question is, why do MOST medics only heal until we stop bleeding (75%) if they could heal us up to 100%? That could be the difference between getting shot once and dying, or getting shot once and having 25% health.

My guess is that either me or them don't comprehend how the healing system works. But I don't rule out the possibility of them knowing it and it being a strategy (maybe one doesn't actually need 100% health and healing would just take more time than needed).