Let me count the ways

Because they dont send the ordered part mine was wrong my neighbor in our tract order was wrong - the shipment here to lake havasu were more than a week late - most likely because tythe phoenix hub didnt have a truck going this way. Well too bad..

In my case they allow you to order parts that are not available and they don't know when they will be available to ship.

On hold for a LONG TIME and stupid annoying hold music angers the customers

Because they suck at customer service...

Because they are a terrible and dishonest business that doesn't care about their customers

Because they are a truly terrible parts ordering website, with average (At best) customer support.

I think they're trying to improve. Summit couldn't get my part either. Bot jegs and summit refunded with no problems.

Because of their mistakes and poor customer service

Because, by their own admission on their website they brag "80% Customer Satisfaction". That means that 1 out of every 5 customers are not happy. The odds are pretty good that you will be the "1".

Honestly I haven't had a bad experience yet, only had one faulty part they ask for a picture and exchanged it for a new one at no cost except the wait of course, they are very polite and have good quality products I am located in the US and have lived in several states and had no change to the positive side in any of these

Idk I guess it depends on your location and or what you ordered.