Also apps do get updated, and when they do they sometimes grow by almost a 100 MB. Repeat that X times, and the RAM on the phone turns out to be insufficient for larger apps of the new now.
Facebook app was 600MB on my girlfriend's phone. Unbelievable. What the hell does Facebook need 600MB for? (granted it was the mostly the data but it made her phone run like crap because the data is stored in internal storage, not on SD card). I cleared the data and it was back to 150MB in less that an hour. So off course people feel like their phones run like crap with apps like that.
I mean even a $50 phone today is extremely powerful for its price, but developers have no consideration for mobile constraints (then blame web techs...).
This anecdote is hard to believe (the slows the phone down part) because unless the app is constantly hammering the storage system with I/Os even as a background process, storage usage doesn't mean it's actively slowing the Phone down. Also it turns out that caching people's photos, etc., will save a lot of bandwidth and improve loading times (especially precious on mobile). Those JPEGs add up quickly...
Honestly I don't know how much consideration devs are actually paying attention to when most of them are probably using fairly recent high-end phones instead of the super cheap low-end mediatek android phones.
I've also noticed that low-end android phones tend cheap out on storage since most people only care about the size of storage not the speed.
Cache. Phones have limited storage, but they're also limited by bandwidth, latency and power. If the Facebook app did no caching it'd run slower, consume more battery and eat up the data allowance of people on limited plans.
