That's a separate issue though, on a rainy Sunday in winter the options for small kids are limited but as they get a bit older they can amuse themselves at home. Once they hit 5 they get into colouring and lego etc and that's a God send.
Personally when my fella gets a new lego kit I make it up and then he breaks it apart and re makes it to his own liking, then when he's not looking I redo it as per the instructions and so on.
I was more just responding to your question "who wants to spend their Sundays wandering around a soulless retail centre anyway?" by highlighting that there are occasions when doing just that is a welcome reprieve for us. I'm not trying to say it is a justification to build one or anything ridiculous like that.
Lego is the job. My youngest has the time of her life smashing up my creations.