What are they teaching - that marriage revokes a will or that divorce does? I can see why divorcing the person your will leaves everything to might revoke it but
marriage revoking a will doesn’t make sense to me (except perhaps to give the spouse what they have received with no will)
Ontario was similar until quite recently and remarriage no longer invalidates a previous will, but oddly a divorce modifies an existing will by removing any reference to the former spouse as a beneficiary or executor as if they never existed.
If the intent is still to leave a bequest to the former spouse for whatever reason, you need a new will post-divorce decree.
Hey, I never took Stiffs and Gifts, and napped through the bar review some 38 years ago! 
I’ll have to see if there is any such clause in our will - which we cobbled together from publicly available forms. But I guess I figured that if I DID get divorced, I’d be astute enough to realize I needed to check to ensure that my will reflected my intentions.
Life insurance as well. Change the beneficiaries!
IRAs, 401Ks, and other retirement accounts also have beneficiaries. I work for a city, so I have a 457 account. Every time there’s a training given on using our 457, the administrator begs us to keep the beneficiaries up to date. We hear stories of exes who got the 457 because the change wasn’t made years after remarriage and a second family. The administrator has no choice but to release it to the named beneficiary.
In many cases, a person can specify the heir or beneficiary as “my current spouse” rather than the spouse’s actual name. It’s unromantic to do it that way, but it means that the person doesn’t have to redo everything if they get divorced, widowed, or remarried.
I agree with you and everyone else that this doesn’t happen anymore (did it ever?).
But…hypothetically speaking:
Could I write into my will that anyone named in it must gather in one room for the reading on the same day and, if they are not there, they don’t get whatever is specified? (As an aside…would the estate have to pay for travel or can you leave that to the beneficiaries to cover on their own?)
Asking for a friend.
And could you require heirs to spend the night in a haunted mansion in order to collect?? 
Hmmm… In California, we’ve got the Winchester Mystery House and the Queen Mary, both of which might be interested in catering to a few more tourists… Might work…
That’s still a great way to whittle down the heirs.
From what I’ve read in this thread, it is the nation of Hollywood of which I am, apparently, a loyal citizen. LOL
Yes! My father died intestate, which was bad enough, but he’d also neglected to make his latest wife the beneficiary of his secondary life insurance policy. Her predecessor, who had been married to him for sixteen years, took this to mean that he’d wanted her to have it because he knew she’d distribute it between his kids. She collected on the policy and divided it four ways between us, and we all then turned the money over to his widow, who was in real danger of losing their house without it.
It probably depends on the state, but in my state, a prior will is revoked upon marriage. It is the law. The whole will. You either have to reexecute that will after marriage if you still want it, or if it was executed close to but before the marriage, it can include information showing it was made “in contemplation of marriage,” in which case it isn’t revoked.
The idea is that you might not have made arrangements for your now spouse in the old will. Either you left everything to friends, family, and/or charities, or possibly to your children and former spouse if you were married before. By revoking the prior will, you either have to consciously choose the new beneficiaries, or your estate will be distributed under your jurisdiction’s intestacy laws, which will mean your current spouse will be provided for.
Here’s an example:
There are slightly different things that typically happen upon divorce.
Interesting. Thanks.