I guess it comes down to why you collect and what hooks there are for certain items or lines.
The Last 17 (and for me it's 17, not 15 although I understand the arguments) have a number of hooks:
1) Yak Face - the only L17 I (remember I) had as a kid. Hated it. My brother and I both had one and laughed our heads off when the first person to the box of figures at the car boot we sold them at excitedly handed over £1 for both the Yaks. "Weirdo!" we thought
2) Nostalgia. I never knew the L17 (bar Yak) existed until around 1993/4 when I got back into collecting. It was the Tomart price guide that introduced them to me. I was blown away by the thought there were another 16 figures I had no recollection of (although a diary reveals I had both a Paploo and a Warok, I have no recollection of them). I was so excited. And every time I bought another collection through Loot the excitement of seeing an Imperial Gunner, Amanaman or Yak Face never diminished. So damned exciting.
3) What they represent. So much! The end of an era of toys that has never been seen before, since or ever will be. Fact. Also, the end of my childhood proper: from there on came computer games, divorce (not me, my parents), **** time at school and the car crash of a remarriage my dad went through. OK, bit heavy for here but deal with it
They also hold an air melancholia about them. Kenner knew their time was up. Lucas had finished the Trilogy but how could they breath new life into an 8 year old toy line without movies? I know, let's release a big lizard, two old women and a baby-headed Stormtrooper.
Some of the sculpts are great. I happen to love Amanaman. Some aren't. Never considered Barada as the forerunner of POTF2, but you're absolutely right!