Stands are parabolas. ie 'like a banana'. Start off shallow, then get steeper and steeper every say 20 rows. It's how they get what they call c values, which are sightlines.
So they have to be shallow at the bottom so that you can reach maximum steepness (34 degrees) at the top.
To get more tiers in then you will have more smaller tiers, plus the shallower the bottom one is the closer you can get the higher tiers to the pitch.
Personally I prefer shallow stands as it gives it more of an intimate terrace feel whereas steep stands fans are less likely to stand. Steep stands with loads of tiers like that Vikings one are good for side stands as they don't create the atmosphere. They're not not that good for End Stands though as it's hard to generate that initial noise if fans are too split up.