The tickets are used to go to different places when using the PC option. For example when you just use the PC option, you just go to the usual TamaTown. But when use your Berry Town Tickets, you can visit Berry town. Same goes with the other tickets. All the tickets that you can get on EnWarehouse are for traveling to e-Tamago ( The Japanese TamaTown ). But since e-Tamago is gone, the tickets are practically useless.
The tickets doesn't decrease because you don't actually "use" them. You can use them or access them by going to the PC option and if I'm not mistaken, the second sub-option. You will the proceed to the Login screen.
Tickets won't affect the items available at EnWarehouse because all of the items are available by default.
Hope I helped