I think that mixed in with the totally pointless changes like rounding box edges there are others that help ebay achieve its insatiable appetite for data on everyone who uses the site. 

How many of us who use the boards are aware that everything we do is counted and measured ?   The number of posts, solutions marked as accepted in answer to their question, or accepted by someone else in answer to theirs.  Kudos given and received and the number of new topics launched.  Ebay publishes those numbers for over 400 contributors to the SC board, but probably records them for many more infrequent contributors.  But why bother just to produce a 'Most helpful authors' board?

Because if they can do that for a minor part of ebay, imagine how much more they can glean by recording other activities when listing, buying and selling.  Every time they think of a way to improve what they can extract from users it might well look like change for changes sake, but in some way it helps ebay's understanding of its users and in all probability can be monetised to benefit ebay in some way.  Data is valuable.

Just as ebay gathers data about its users, others gather and publish data about ebay.  How much foot-fall per day.  How many visitors bounce in and out in seconds.  How many visits result in a sale, or don't.  How long is the average visit and how many clicks are made while here and many more stats. that I can't even think of.  Seconds count and are valuable.

To make ebay look bigger, better, more successful and raise it in sector Ranking Tables, it's in ebays interest to lengthen time spent here, by introducing acres of space between buttons, hiding drop-downs etc.  Changing something from a one click on one page action into a multi-page maze requiring multiple clicks, shuffling left and right (the Selling pages) is for ebay's benefit, not sellers.

Every second that a user is confused, wastes time going round in circles or clicking between multiple screens where there used to be one, is good for ebay.  Simplicity, efficiency and being user friendly count for nothing when time wasting, complications and confusion raise ebay's profile in the rankings and the share price is influenced by ebays place in them.

Isn't that why the 'improvements' come so thick, fast and seemingly pointlessly ?