(Just my general POV of why some biz's dont offer smaller sizes, not halo alone)
I've found that there are Very very Few juices I order more then once(maybe
three flavors in 8 months of
vaping), most are just "eh" or I like them but dont reach for them that often.
So from a biz POV it's better to get you for a full size once then ten little ones.
Cause if you dont get hooked...well they already have your money.
If you do get hooked, what difference does it make...your coming back just the same.
Plus realistically it's just as much work to create a small bottle as it is a big one.
As far as driving more new biz to the site...none of these folks are really hurting for new customers. If you want to try it bad enough, you pay the full price for it...or snag a sale on it.
However there is another source of samples....keep an eye on the classifieds and check out the PIF forum. Might be able to get some there.