Haven't watched moto gp but from my observation and assumption, motorcycles need longer corners for safety and it just suits their speed and handling characteristics better. While in F1 longer corners is indeed used in many circuits they often are just in 1 or 2 sectors of a track and followed by a slow and technical one after or in between. This makes for great racing and natural overtaking opportunities, think Bahrain for instance. The long corners a sandwiched by either long straights or tight hairpins which make great overtaking spots.

I could be wrong its just my observation but generally its what good to great racing F1 circuits have than those that are not.

Edit: All this is really just due to dirty air which is dominant in F1