God has to keep an eye on #everybody all the time# to see that they are being good (according to whatever current conventions are).
Satan just has to wait until said people 'one minor offence from a long list' is committed (no matter how many or how few such offences are committed thereafter).
God requires eternal praise from those in heaven.
Satan makes no such requirement.
Another view of the devil
Among polytheist religions have both gods and goddesses (and various other entities of varying gender(s)), and there is much argument as to whether God is male, female or 'more complex.'
However 'the Devil' in the modern sense is normally seen as male. (Hel, Proserpina and the succubae are different sorts of entities).