Hummm…
good question.
But it may be that just the bells are silent (as are the bells in the Church … for example one may have had the ringing of bells at the procession of the Holy Eucharist on Holy Thursday…but today on Good Friday at a Monastic liturgy I attended they had wooded “clappers” …no bells…
I have never heard of not praying the Angelus on these days…
And the ending prayer has to do with the passion and death of the Lord as well…
I prayed it today.
Of course there is the change at Easter!