Lighter colored hair does not reflect as much light as darker hair, so even though it has the same "shine" as darker hair, it will not be as noticable.  This has been my frustration for years and years.  My dark blonde, light brown hair never was shiny enough for me. 

However, over the past 3 years I have quit using products that build up on my hair.  No more -cones or heavy conditioners.  No chemical treatments.  I protect the hair from abuse.  I oil my hair with jojoba oil on a regular basis.  I wash my hair less, which allows the natural oils to stay on the hair to protect it more.  This has resulted in hair that is healthier and has much more shine.

Don't forget that a vinegar rinse will bring out the shine in your hair.

The straightener might give the appearance of shine by aligning all the hair in the same direction, but anytime heat is used to accomplish this, the hair is not being made healthier - in fact it usually is damaging the hair by drying it out.  If you use heat on your hair, be sure to condition the hair to replace the lost moisture and use as little heat as possible so that you don't cause too much damage.