There are lots of theological reasons for Good Friday being an aliturgical day. Most of all the solemn events without an actual Mass show remind us that because of our Sins, Christ left us through His death, He was absent from us that we may have forgiveness of our sins. We mourn His Death, because it was a real suffering and death, not as the Gnostics claimed just the appearance of death.
As to the posting of Fiddlebacks, well the truth be known, (And don’t get me wrong I prefer the Roman Style and Fiddleback, I prefer it to Gothic.) But the Fiddleback is a newer style of vestment. Around the turn of the last century the Gothic style made it’s return after a four hundred year period where it was almost forgotten. The only ones who retained the older style were Trappists and other strict orders who retained the simple vestments which pre-date the Fiddleback. Sadly it has come to be identified as “Traditional” by many as more traditional than the older gothic style.