The refresh button in resources could for example send an empty dummy transaction so it would refresh the CPU and NET, since on EOS your CPU and NET are refreshed only after transaction, not periodically.
This is bad because:
If I rent 50k EOS today and spend all cpu and net power, and tomorrow I only need to rent 10k EOS from PowerUP then I have to rent over 50k because renting power from powerup does not refresh the CPU and NET. So I have to rent 60k, just do to 2-3 transactions and “refresh” my power, and then I’m left with loads of power unused.