If online is the only place you can get them & you want to buy...

If online is the only place you can get them & you want to buy them you'll buy them online. Even if they stock them in woolies there are plenty of people who still won't be able to buy them.
The margin selling direct will far exceed the cost of the portal vs via Woolies. Yes the volume online will never be massive but it's a no brainer to set up an online portal which costs peanuts.
Personally i think retail is a hassle that's not worth doing when the opportunities in the commercial sector are so big but to say people don't buy sanitisers online is ridiculous. They sell them via Amazon in the US!