Exactly what 18DAI says.
Bottom line... dollars.
Cheaper to manufacture (like Glock) and still charge about the same price. Mucho profit compared to manufacturing steel or aluminum frames).
The LPA's I have on two of my Tanfoglio Witnesses, and one on my SIG P226 have been very reliable (never broken) and very easy to use/adjust. I would not hesitate to by them again for any of my pistols.