Very few investment trends have caught on as rapidly as model portfolios which have seen widespread adoption, but this could be lowering asset flexibility. Model portfolios seek a variety of metrics for assets to be added to the fund. Assets may be excluded for categorical or qualifying reasons which can lead to a lack of adoption and lower returns. The selection bias in models leaves meat on the bone for investors and can keep them from getting exposure to products like covered calls or other investments.
Finsum: Model portfolios have their place, but they could create an inefficiency where some products are given their proper value.