1. No matter the size,  I doubt a store can meet all the needs of every customers.

2. As per your example, buying 10 different items in Harvey wont be cheaper compare to 1. Convenient ...yes.

Usually get from few stores so it can fit my requirement better.
Furniture maybe just a couple..

Electrical item depends..sometimes warehouse sale cheap.. sometimes online cheap but cannot do time guaranteed..offline store can deliver big things w their own lorry subcon so can time guaranteed delivery, I'll take that coz I have delivery time restriction.

IF its electrical stuffs i suggest you get from the same shop (Harvey Norman/senheng) and get a bundle discount. you can negotiate further if you are good in negotiation. it'll be much cheaper compare to you buy individually *from my personal experience

for furnitures, i don't think you can get what you like from the same shop.

Replacing a blender is more costly than replacing a washing machine, so most would want to fix a washing machine.
I had a panasonic washing machine for 8-9 years and it had started to leak. It was very good in other ways, I called Panasonic, a technician came the next day.

I have problems with my Sharp fridge, they tell me to take it to their centre. A 6 ft 2 door fridge. I don't call that service. I knew many 3rd party technicians in my old place so didn't know about their unfriendly service. But now, no more Sharp stuff for me.