I bought those "quilter's must have" yellow quilter's pins many years ago and never used them. I've been quilting steady for years now. They are so long and unreasonable for piecing 1/4 inch seams. So what are we supposed to be using them for, does anyone know? I use them now to hold fabric to the back of my little fabric bolts.

I use mine - but then again, I don't think I pin the 'normal' way.

I sometime use them when machine quilting to add extra pins just before the pressure foot. Especially when the fabric looks like it will bunch. Have to be careful of the points.
There is a product on the market now that looks like plastic ear plugs that the "inventor" show how to use the longer yellow pins to baste and protect the point by pushing the ear plug on to it.
Otherwise they are useless to me.

I use them to hold together my top, batting and backing when I quilt.

I have some too that I don't use for quilting...maybe to pin borders onto quilt...but not for any piecing. Lately I have been using some to apply glue for some projects and throwing away after (instead of using toothpicks)...at least then I don't feel the guilt of just throwing them away.

I don't like the round yellow head pins called Quilter's Pins. they are too thick and not very sharp. I use the glass head pins, very thin and sharp and some have yellow heads but you can tell the difference by the price. Fons and Porter has short and long glass head pins that are great. Clover pins are excellent too. Once you use a great sharp pin you won't reach for the yellow headed pins again. I do like the yellow flower head pins.

I use the white glass head pins.
They don't melt under the iron.
Their extra fine.
I got them at jo-anns.

I like them, but find I use them mainly when doing large piecing & even use them for regular sewing instead of normal straight pins. They don't get lost like the small ones do. I find the flat flower head pins are nice & really like the small glass heads for small piecing & curves. For smaller quilt projects, like tabletoppers & bench covers, the yellow head pins work to hold the layers together better than safety pins & because the heads are large, they are quick & easy to remove while machine stitching. So I'd say having an assortment means you'll have the right one at the right time.

they're great for frame quilting

If it's the flower head pins, they are great for pinning a pattern or whatever you need to cut around & still be able to use the acrylic rulers. They lay flat & your ruler doesn't teeter totter back & forth when you are trying to hold it down. As for ironing with them, no, they melt!