The convenience issue is definitely the sticking point with any reusable container concept. I think a cost incentive will overcome this barrier for most people, though - and I'm fairly certain that single-use sachets are much more expensive per gram of product than buying in bulk. The question, then, is how to support low-income consumers to adopt the bulk-buy in reusable containers system? It seems one of the advantages of single-use packets, besides convenience, is low-cost because some consumers do not have the level of cash-flow required to buy in bulk - they only every have enough cash to buy their daily needs. Perhaps the reusable container concept could be combined with micro-lending or a subscription based model to help those low-cashflow consumers to adopt the system?