We would like our Crocus flowers to look like the image on the left, but what if it is more like the flowers on the right? Perhaps you selected your Crocus bulbs to have lovely striped interiors which you didn't see, other than the odd glimpse.
Crocus flowers are sensitive to light. They close their petals at nightfall and open in the morning, but only in the right conditions. If Crocus are not planted in a sunny spot, or sunlight is scarce because of a poor spring, there will be a poor display of flowers.

In botanical terms, this is called nyctinasty. It is associated with night and day, but Crocus also close their flowers  ( video) when the light is poor. Other common plants which do this are Tulip, Californian Poppy, and Morning Glory.

If you want a really good display from your Crocus bulbs, it is essential to plant them in a sunny spot.