Question of when to use fast and/or express belts

[Targa]

Hi all. I've been trying to wrap my head around the concept of the fast and express belts, and am a bit confused. As far as my brain's logic can tell, faster belts are only useful where a bottleneck might occur (such as a bend or curve in the belt). As an example, let's say an ore miner is mining 1 ore per second, then no matter what speed belt you use, your smelter is only going to receive ore at a rate of 1 per second (maximum), hence, the practice of upgrading all your belts to faster belts is a waste of time and resources, as far as I can tell. Can anyone provide some insight as to when and where, and perhaps how, faster belts are useful? Thanks!

[kingarthur]

the first beneficent of the red and blue belts is that they are faster and have a higher max throughput which can allow you do do things like replace many yellow or red belts with fewer belts at faster speeds. they can also move items around faster so they can cover distances faster. if different belts are mixed in certain ways you can compress items together or open gaps so inserters can place items down. as you say in the op if one miner can only mine 1 ore/s to give it to the furnace than there isnt any point but they come in handy when you have say 25 miners or 50 or 100