Almost all red wines that are found in the middle price range and down are put through a -3°C cold chilling process for tartrate crystals to be made stable and then sterile filtered.In the top end price range, red wines that are kept for at least a year in barrels, this process is not done as most of the tartrate crystals precipitate out over the winter period and can be seen against the side of the barrel. This is softer and more natural than the chilling process however it does mean that there will be crystals remaining in the wine and this will with time find their way to the bottle sides or base during maturation.
Aligned with that there is no need for a sterile filtration to the wine which can remove valuable wine flavours. As the crystals precipitate out they attract some of the colour compounds as well thus we see the crystals as red in red wines and white in white wines.
The fact that there is a sediment in the red wine is a sign that the wines were not interfered with artificially and thus show more uniqueness and complexity. Decanting these wines is clever for more than just leaving the sediment behind but for the subtle aeration that occurs as well thus enhancing the value of the wine drinking experience.