I've had decent experience in actual play with summons in exploration more than in combat, as you noted with the crawling hand as an example, but also with ferrying party members around or general roleplay opportunities to help with getting/gathering information once you can summon more talkative creatures.
In combat I'd have to echo the soaking hits being their primary use. Something makes it through the front line, I have small or narrow passageway or anything similar and no wall spells prepared or available I'd fall back on the creature to substitute.
I definitely agree that they're not powerful by any means, but I don't think they're without uses, especially with spells on their level for the diverse utility they can provide both in and out of combat. In combat I liked the whiptail centipede just for the reach, space it took up despite being able to squeeze well and poison being a nice deterrent if things got to close to my squishy self, but I think a number of other spells could have worked just as well or better.
My one missed "feature" from reddit! Thanks a bunch.