Excellent point! … unless it is for a good cause - and those causes being completely arbitrary and vastly different between users.
When I started in 2010 I had a 400w array - 2 x 200w panels.
Then I wanted more, could not get the same 200w panels, so I got 3 x 310w panels on 2nd MPPT.
= total potential of 1330w.
Never got even close to that being, at that stage, a off-grid system, because of cabling, small battery bank and just because …
So I sold everything and went grid tied.
Started off in winter with 2.1kw panels. Ran the system for a while, and promptly increase the array to 3.5kw.
Now I need ±500w more in the middle of winter. The cost of getting that 500w extra?
Option 1: Add 5 x 350w panels + instalaltion costs - keeping array 3S/5P
Option 2: Add 2 x 350w panels + installation cost and rewire to 4S/3P
All that now for ±500w exstra?
Issue started because I had a 150/100 when I bought the panels. 2S/5P made sense at the time, coupled with CoCT and max inverter size and all that, in that one could limit the array to meet the requirement , i.e. max of 3.5kw.
Then I had the opportunity to get a 250/100 … if I had that first round, and CoCT was “lit”, it would have been 4S/3P from the start = 4.2kw potential, optional expansion to 7kw 4S/5P - IF Eskom slips any further.