Why do Smoking effect get traded a lot?

Sale 1

http://www.tf2outpost.com/trade/21684070 - Sold for Blizzardy Storm Ol' Snaggletooth + 1 key (18*0.9 + 1 = 17 keys) (Outlier)

Sale 2

http://www.tf2outpost.com/trade/21670703 - Sold for Cloud 9 Tam O' Shanter and 3 keys (1.8*0.9 + 0.16 = 1.62 + 0.16 = 1.8 buds)

Sale 3

http://www.tf2outpost.com/trade/21992390 - Sold for Smoking Bubble Pipe (1.3*0.9 = 1.2 buds)

Mini for Smoking Bubble Pipe

http://www.tf2outpost.com/trade/21958626 - Sold for a Blizzardy Storm Prince Tavish's Crown (1.4*0.9 = 1.3 buds)

But then, 1.2-bud is QS because:

http://www.tf2outpost.com/trade/21930202 - Sold for 1 bud 3 keys = 1.2 buds (QS)

=> Outlier

Sale 4

http://www.tf2outpost.com/trade/21854152 - Sold for a Stormy Storm Hottie's Hoodie (1.5*0.9 = 1.4 buds)

Mini for Stormy Storm Hottie's Hoodie

http://www.tf2outpost.com/trade/21300639 - Sold for a Miami Nights Tippler's Tricorne (1.6*0.9 = 1.5 buds)

Sellers

http://www.tf2outpost.com/trade/22242148 - 1.5 buds

http://www.tf2outpost.com/trade/22101505 - 1.5 buds

http://www.tf2outpost.com/trade/22225721 - 1.5 buds

http://www.tf2outpost.com/trade/22137350 - 1.5 buds

http://www.tf2outpost.com/trade/20417698 - 2 buds

Unused sales

http://www.tf2outpost.com/trade/21983031 - Sold for Bubbling Attendant (Outdated, will base its price on this)

http://www.tf2outpost.com/trade/21550051 - Sold for a ton of weird things and killstreak which if I use SCM here, it will give some weird price.

http://www.tf2outpost.com/trade/21514952 - Sold for 1 bud (QS)

http://www.tf2outpost.com/trade/22136628 - Sold for 1 bud (QS)

http://www.tf2outpost.com/trade/22167658 - Unconfirmed.

Feel free to counter / support my proofs.