Adam, it’s a ‘slight difference’ when you’re talking about the FTSE 100 where the spread is down to pennies due to high trading volumes.
When you’re looking for smaller companies on the lower end of the FTSE 250 and beyond the spread is a lot more relevant. A buy price of 12p with a sell price of 10p is a massive spread, it means your trade has to grow 20% just to break even and this should be visible to newer investors ideally without the need of switching between apps. Not everybody on here is a long term investor.