I would actually ask that of the others who think that GM's are often going out of there way to dick people over who summon them.
Players aren't idiots, they will summon a powerful spirit with edge, resist drain with edge (points well spent when you sometime spend multiple edge just avoiding death in one combat turn) be nice to it then get it to mop the floor with the enemies. They wont act like a cartoon villain with his henchmen.
I'm a D&D player, first and foremost. I ALWAYS assume that any summoned entity with a will of its own is going to be pissy if you mistreat it, and act accordingly. I also never assume that someone won't be an idiot. You ALWAYS assume that there are idiots and they have access to alcohol or hallucinogens as easily as if they have air. Doing otherwise invokes Murphy.
Also, I most certainly HAVE seen players act like cartoon villains with their henchmen using spirits for suicide missions and other things.
Also, what kind of build are we talking about for this hypothetical summoner? How much Edge are we talking about him having? Given the way Priority works, any mage worth talking about is going to have an A on Magic, with B and C going to Attributes and Skills (either order), so absolute max without spending your starting Karma would be a human Mage with 5 Edge who put Resources as E. So you have 5 Edge to spend throughout a run, and you spend 1-2 of it on each spirit you summon during the run. That's cool if there's only one fight the whole run, but by the third or fourth run? How many services are they getting? Are there other mages out there who are trying to banish them?
You've got Resources on E, so that isn't much for weapons, armor, and other gear that a runner needs. You're probably not going to have more than an R1 Fake SIN, which isn't going to pass more than the briefest of scans, and your commlink might as well be an open book for all the good it will do against anyone trying to hack you. Worse yet, you're forgetting the key weakness of spirits: they go poof when you ice the summoner. That's right, you just took "Geek the Mage first" and dialed it up to 11. Those corpsec you set a F12 spirit on? They don't have to beat your spirit. They just have to get enough grenades in your area to make you chunky salsa.
Seriously, what is with you people? It is like the only way you know to fight a big hulking troll with milspec armor is to try and outslug him! You may as well try and punch out Lofwyr.
Anyone that tells you spirits are balanced is, frankly, nuts. A mage can easily have 6-8 force 6 bound spirits very soon out of charged. With a summon that up to 9 spirits at force 6. That means a good mage (not even a dedicated summoner) can solo any mission almost straight out of charge if they do it carefully.
You're forgetting that spirits hate hate HATE being bound. 6-8 Force 6 bound spirits? If your GM isn't actively fucking with the player to make them have each service be worded like a gorram lawyer wrote it, then they need to turn in their GM screen. Malicious Compliance is the order of the day for characters like this. This is what the whole 'Astral Reputation' and associated qualities (Spirit Pariah comes to mind) were written for!
Are you just looking at the summoning rules in a vacuum, and not looking at all the other stuff around it?