I think that most swappers are quite aware that the Arc eagles are lurking on the swap GB's and that their positions are not secure.
I think, for some players - even some experienced, veteran players, it's simply just easier to use the swaps than to bother with all the 1.9 math - and the special "rules" about how to post in a 1.9 thread (editing and reposting GB-lists or however it's done). It's too much trouble. You need a math brain or a calculator, and you need to learn how the 1.9 system works. It's much easier and faster to just make a swap, even if you know it's risky and inefficient.
Agreed, the math is complicated - for me, I made a spreadsheet to handle all the data.
I pre-load one of the sheets with all the need data about a GB - # of fp's to level, all of the gb slot pay-outs, etc.
Another sheet is used to enter the real time data - # of fp's already entered, the slot pay-out, the # of fp's already in that slot(enemy donation), and so forth.
This indicates how much needed to secure, expected amt to be entered by the donator, and such.
With the spreadsheet, doing gb is very easy.
Needless to say, the sheet handles any slot pay-out rate 1.9, 1.3, or any other number needed to compute all slot values base on the rate pay-out. I designed the spreadsheet long before I entered the 1.9 clubs.
It was used to calculate a donation profits while I was leveling my gb's, including my arc before it reached lvl80. This allowed those that were helping me with their 1.9 arcs to also get a profit back (a thing some of the new people seem to think is unfair - how dare someone get a profit for helping somebody while it takes days or weeks to get their donation back) a small price to pay.