When the systems went online, staff were allowed to access their own NI account the once, presumably because it was new and they knew folk were tempted to look anyway.
That changed years ago and random checks, some known and some unknown are carried out daily. If names are in the news, there tends to be checks carried out if claimants with the same names are accessed.
As has been said, there needs to be a valid reason for looking up details online and it's not worth the risk.