I would say both of these show up in messy grappling situations.  A couple punches get thrown, somebody clinches to stop the pain, and they wind up with two overhooks = front overarm bear hug.  You are stand-up wrestling around, somebody goes for a leg or the groin, the natural defense is a wrist grab.  Then the free hand tries to fight off the grab and it gets grabbed = double wrist grab.  

In general, think of these less like standalone "attacks" and more like positions you might wind up in a melee.

Iain often quotes Itosu regarding the unskilled ruffian, but assuming that this is the only kind of enemy nowadays might be very dangerous for us. We should better not imply that an aggressor is unskilled in the martial arts - you find martial arts places on every street corner and on the internet. We visited an elementary school recently and did some padwork with the children and some were moving like boxers: guard up, head movement, leg movement, everything.

But I guess we can assume that the attacker has no real strategy and motivation beyond "I'll mess you up" if we use the term "unskilled".

19 = you bend over, the opponent is in front of you and grabs you around the torso. This scenario is not a starting position you will find yourself in but it may easily happen if you were pushed down after being grabbed at the shoulders or neck (so: from grappling) or hit in the stomach or lower before. Or you tried to tackle and failed. A more nasty and quite life threatening variant is grabbing the neck instead of the body but afair that was another list entry in HAPV (like reverse choke or so). Another variant might be that someone pulls over your shirt in that position, Afair that also was another list entry in HAPV.

In scenario 19 you could be open for a kneestrike or some punches to the sides if the opponent wants to hurt you. But from videos I have seen, holding someone down and randomly punching and hammer fisting as often as possible is the most likely choice. You will probably hold on with enough force and counter movement that the opponent won't get the idea of kneestriking (and they are not necessarily willing to escalate to that level of violence). Otherwise this may also be an intermediate stage before going to ground - like the opponent grabs you and just drops weight in hope you go down.

24 = A reason for doing so might be to show dominance ("what are you going to do now?!"), it may be a try to move you or hold you (freely or against a wall). The usages of that action might not be super sophisticated but the situation sometimes just happens. We had that in school quite often: we pushed or grappled after talking enough sh*t and sometimes someone just grabbed both hands (to make it worse: with just one of his own hands). There were no real follow up attacks ever, because nobody was willing to escalate higher and most people were not able enough to get free unless they were stronger (that was just unskilled force against unskilled force) so it was clear who won and the matter was settled.

Well to answer your question directly for me 19 is a mixture of intentions ; at close range a ‘charge’ at speed to get the person on the ground (which happened me but I was lucky and turned and caught him with a sort of propping / drawing ankle throw), a pin against a wall or over a car bonnet or as part of a gang robbery attempt. However I have seen an attacker getting a battering and then try and stop it by using 19.   24 is a hangover from the times that swords/ short daggers were carried; so griping both hands to prevent the weapons from being drawn this grab done so at close range/ when walking past. It features in the Judo GoshinJutsu kata. Hence the legacy- I would even argue its not habitual the dictionary definition  of Habitual is ‘constantly, regular. Usually’.  I would say a punch/ blow to the head/neck region is habitual in fact statistically it is,  certainly in the UK hospitals admissions as a result of violent assault mainly due to fists and kicking the victim when on the ground.