the ssd's are great for portables , lighter and you dont need much storage in a portable , and normal sata harddrives cost next to nothing compared with a ssd thats the only reason ,and still most people prefere as a option a 2 tb hdd in their AIO desktop rather then a fast 128gb ssd and the 512 gb ssd in the macbook cost over £1000 which would double the price of the iMac
another thing apple could try to find a space inside for a ssd and a hdd , a small 64gb ssd which is affordable for the os and apps would be enough for most people and storage on a hdd