Yep, 100% agree that it is annoying and frustrsting, but I wonder how many of those sellers are new?
Some really do not understand the bidding / auction process, and even start with eBay's ' recommended 99p start'.
All you can do if the seller cancels, and does not fulfill the transaction with the posting of an item won in auction , is to contact eBay Customer Services explain the cancellation was not authorised by you.
eBay will place a damaging defect on their account, it doesn't take many, especially if they are new, to have them removed from eBay's selling platform.
Or, they may learn from it, and start their auctions for the minimum they wish to receive, then there can be no disappointment for either buyer or seller.