1) There are two reasons. the first one is, if both the strands are copied, this would lead to the production of two different types of mRNAs , which means, two different types of amino acids would be formed. This would certainly make the genetic tranfer machinery more complex.
The second reason is, if two types of mRNAs are produced, they would be complementary to each other, and they'd readily combine with each other to form dsRNA (Double stranded RNA). This means, the process would be a futile one.
2) In bacteria, the process of translation begins as soon as transcription begins. That is, there is a very small difference between the beginning of the two given processes, in them. So, they can be coupled - translation will begin as soon as translation begins.
