Some of the changes in permissions are to allow new features with the update of the app. If the app has a display that needs to be seen it is going to need to prevent the phone from sleeping, Modify/Delete SD card contents is to allow the app to save what to the SD card instead of the limited amount of memory on the phone. Yes, sometimes they are fishing for advertisers. When the update comes up and you go to the Play Store to update, if there is a change in permissions you have to agree to accept those or abort the update. It is up to you to decide and each permission change is listed.
I just update the apps. What I object to is so many updates - and usually of the same app within days of each other.
If only OS platforms and software publishers did that, though, instead of saying, "You bought last year's version and now we fixed and or improved it - so now you can buy this year's version." So far no one has asked me to re-purchase a new app for its updated version - they just give it to you.