Sounding out the words seems slow. Would it not be faster to memorize sight words?
Blending sounds to say words may seem slow at first. But, it is the fastest way to learn to decode! Mixing reading strategies (sounding out, memorizing, guessing, etc.) is confusing for many beginning readers. The Sound-to-Print connection is the most critical sub-skill for reading. Taking the time to build this sub-skill will make fluent reading possible!
Should the reader understand the stories?
A high degree of fluency is needed before the reader will be able to remember the sentences. Fluency is not expected during this time. Reading fluency is a characteristic that is developed after the Sound-to-Print connection has been firmly established. Re-reading the sentences by a teacher / tutor / parent can be used to help with reading comprehension.
Why is reading English so complicated?
English spelling has a long history. It would be easier to teach reading if there were only one symbol (Letter) for each Sound. Sever features (using multiple letters for one Sound and using those same letters for more than one Sound) in English spelling do complicate the reading process.