Given his TFSA is entirely maxed out, it is not necessarily true that he shouldn't contribute to his RRSP; the benefits will just be smaller than they would be under different circumstances.
The benefit of an RRSP contribution today, is an immediate deduction from his income on this year's tax return. The penalty of an RRSP withdrawal in the future, is that it will be added to his income in the future.
In simple terms, he gets the time value of those tax savings today [instead of investing his money in after-tax dollars, he invests more money now, because those dollars invested haven't been taxed yet]. But if his income will be higher in the future than today [or, if income tax rates increase in the future], he will lose some / all of the benefit, because he will pay higher taxes later on.
The second benefit of the RRSP, is that every year, he gets the compounding effect on all of the additional earnings he was able to contribute because he hasn't paid taxes yet. So if he contributed 20k [when he would have contributed 16k before tax], then in year 1 he gets the earnings on the extra 4k, and then in year he gets the earnings on 4.2k, assuming he earned 5% in the previous year.
If he chooses between his TFSA and his RRSP, the TFSA probably wins out if he has a short time frame until retirement. Otherwise, his RRSP will give him some amount of benefit unless he expects his retirement income to be higher than his current salary income, or unless tax rates increase in the meantime.
Note on the benefits - if he dies before withdrawing all of his RRSP, that money is not lost, it will be passed on to the beneficiaries in his will; this is not like CPP income. If he wants to enjoy the benefits of that money entirely, and doesn't want to leave anything behind in his will, then of course, saving money for retirement creates that "risk". The benefit, of course, is a larger nest egg to sustain him for a longer life.