For sales, yes, it is a basic need and has always been supported, but for purchases all that really matters is the totals. The purchase side of QuickFile is set up around the assumption that you’re recording transactions for which you have been sent an invoice or receipt by a supplier, that invoice or receipt is the primary record and all QuickFile needs to record is the total (net and VAT) for the transaction, optionally broken down by category if it’s a purchase covering different things.
Having to enter unit prices and quantities is a pain in this case, you don’t want QuickFile to calculate totals for you, you need the totals to match the invoice from your supplier.
Purchase Orders are different, there the quantity column is supported because the purpose of those is different, they’re a document you send to your supplier to tell them how many items you want to buy, rather than a record of how much money the supplier charged you when you bought them.
There is a feature request asking for the quantity field to be an option on purchases but in most cases it’s irrelevant.