They gave up that fight about two years ago... Most
people observe a generic "no cellphones in indoor public places" rule. But they forget to turn their phones off. So, the internal math is "I meant to
switch my phone off, but I forgot, and this is an exception. I ordinarily never do this, I am so embarrassed,
but you all understand right? This is an important call. I'm so sorry... If I leave the computer, it'll log off automatically..." They have that little imaginary conversation with everyone around them and it excuses it...
Then again, there are some people who don't care. They just pick up their phones and start yakkin' at FULL VOLUME.
The war is over. I have discussed this with the library staff, and they said that it caused more problems to point out the policy than to drop the policy. What happened was, one staffer would be a no cellphone crusader who would point at the sign, or carry it around showing people, or just directly ask people to take their phone calls outside. Then the cellphone people would comply, come back inside and start YELLING... "That was a VERY IMPORTANT phone call! I have children! Emergency! I NEVER would ordinarily
but this was an exception! How dare you! My Uncle had a heart attack!" And so on and so forth. It wasn't worth the effort.
So the people like you and I, who dislike it don't YELL... squeaky wheel gets the grease, I suppose.