That's precisely why you don't receive any vouchers! Vouchers are sent to those that don't buy in order to try encourage them to do so...
I have two accounts on Takealot. One which was from Takealot, and one which was from Kalahari (different email to my takealot account). I refuse to buy off of the one account! So whenever they send out these vouchers, my one account always gets them. When I say "them" I mean about 4 x R100 vouchers, every single time! Some people get a R50 voucher, others get R100 vouchers. My account always gets the latter!
The thing is, these vouchers are not locked to your account, so I use these vouchers on my regular Takealot account. Although they limit it to one voucher per account, I'll just use another voucher on another family member's account. Point is that I never buy anything off of my ex-kalahari account and as a result, they always send vouchers to it when they run these promos...