Is there a problem creating only differential backups every hour?
Storage is not why you take log backups.  You take log backups when the database is in full recovery model, and you need point-in-time recovery between full or incremental backups.

If your business can afford only 1 hour of lost data, then I'd typically setup nightly full backups for smaller databases, with log backups every 30 minutes during business hours (or even 24-hours per day).

If you had the database in simple recovery model, and each database was only a couple of hundred megabytes, you could simple take full backups every hour, or half hour.

Essentially, the decision comes down to answering these questions:


What is my recovery point objective?
What is my recovery time objective?


See Wikipedia for great details about what those two things actually mean.

If you're storing high-value, business-critical data in those databases, you should understand log backups, and the transaction log and recovery in general (link to my blog), to avoid being in a situation where you're unexpectedly missing data, or down for an extended period of time.

In your case, I would also do a log backup after every diff backup just to ensure the log doesn't grow out of control.