Native English speakers speak with the goals of:
efficiency (meaning they say the most they can in the shortest amount of time); and
using flow and music in their speech.
Something that may interfere with these goals of efficiency and music in English is the appearance of consonant clusters. This is when three (or even two) consonant sounds appear together in a word.
Example
The word “spring” [sprɪŋ] begins with a consonant cluster, the three consonant sounds [s] [p] [r].
“spring”
When consonants clusters appear at the end of a word in English, they can be difficult to say, even for native English speakers. In order to make the pronunciation of these words with consonant clusters easier, and more efficient, native English speakers unconsciously:
delete the middle consonant sound; or
transform a sound to use less movement of the tongue.