Sometimes it's a question of choice...or lack of choice.
I live exactly between 2 branches of Screwfix, one is 14 minutes away, one is 12 minutes away. If something is out of stock in one branch, the other usually has stock. my next nearest is 20 minutes away. All have a Toolstation virtually next door, one has a CEF outlet which has virtually no stock of anything I want, and the staff might as well be in Greggs for all they know about electrical stuff.
Thus, I have no choice really. having said that, if I browse carefully I can usually find what I need/want, and at a good price. I often check Screwfix and toolstation, not for a cheaper price but because one or other may have a slightly different item that is more suitable. I don't go on price but suitability. For example, all-round band/galvy-band/whatever you call it...Screwfix do a range, Toolstation do a slightly different range. i carry 4 varieties, 2 from each supplier. It's cheap as the proverbial, but slight variations make having a choice useful.
There really is nowhere else for me to shop, except B&Q, which is part of kingfisher anyway, and often in there you can see Screwfix stuff, but at a higher price. The only advantage with B&Q is if, for example, you are looking for sockets to match existing, as they have the whole range on display so it's easy to check what you are buying. Of course, never ever rely on the labelling on the shelves or on the packaging, or you will find the back-boxes you bought are not as deep as you wanted!
Both Screwfix and Toolstation are great for returns...no questions asked. Like them or not, this is retailing at its best for now, with plenty of shops, long opening hours and a huge range of stuff. Like I said, I have no choice really, but do i need any more choice? Not really. They may have cornered the market, but frankly they deserve it, having pushed other less efficient suppliers aside in many cases. However, I still regret the demise of some independents for tools and basic ironmongery, like catani and crocketts (Glasgow based) and of course, Bill's Tool Store. I recently went to a specialist company who could provide me with specific fasteners I needed for a repair to a machine. I took the old "bolt" to them because nobody else stocked the exact same item. The guy looked at it and offered me 4 different options...steel, stainless steel, aluminium, or some fancy coloured stuff. I went with the s/s option. How many do you need, he asked? Actually, just a couple, thanks. he came back with 6 and said "Here you go, no charge, it's not worth opening the till!"
Maybe it is a shame that the big names have stolen the market, but they do so with rigour and a huge range of items. That's what we need, what we want, and what we will always value. hate Screwfix? Tell me where else I can shop for everyday items. Specialist tools, Axminster etc are great. replacement parts, well, there's loads of those too...Saxton do great multi-tool blades, parts direct and others with similar names do lots of little bits n bobs you can't get elsewhere, and some even do genuine cordless tool batteries at half the price of Screwfix too! I refurbished my favourite, 35 year old black&Decker Workmate including the rubber feet and the plastic leg stays and steel hinge pins for £14 from a specialist spares company, and a new priming bulb and diaphragm for my hayter lawnmower for a tenner. Yes, specialist stuff needs research, but bread and butter stuff is a Screwfix or Toolstation buy for me. Really odd stuff I get from the big river etc, but everything else is from the guys nearby, and if i take it back, the refund is pinged to my bank account by the time I get back to my car.