It sounds like concern is some kids are applying to many colleges that they do not intend to attend, which hurts your kid’s chances of admission.
Colleges need to admit a certain number of kids to fill the class. The number of admits does not need to be constant, but the class size needs to be. If an increasingly small portion of admits plan to actually attend, then the number of admits needs to increase to keep the class size constant.
However, at the colleges that are typically considered highly selective on this forum, the opposite trend has occurred. Admitted students are more likely to attend over time, leading to yields going up over time. Some specific numbers are below, comparing current yield to yield 10 years ago.
Stanford – 2008 Yield = 71%, 2018 Yield = 82%
Harvard – 2008 Yield = 78%, 2018 Yield = 82%
MIT – 2008 Yield = 66%, 2018 Yield = 76%
Yale – 2008 Yield = 69%, 2018 Yield = 70%
Princeton – 2008 Yield = 59%, 2018 Yield = 69%
Penn – 2008 Yield = 63%, 2018 Yield = 67%
Columbia – 2008 Yield = 59%, 2018 Yield = 62%
Brown – 2008 Yield = 55%, 2018 Yield = 61%
Cornell – 2008 Yield = 46%, 2018 Yield = 60%
One of the contributing factors to this trend and the relatively high yields listed above is an increasing reliance on early admissions programs that are often restrictive (ED1, ED2, REA, SCEA, etc.) and often giving a strong preference to such applicants. This is an easy way for your kid to show that he is truly interested in the school and not a high stat kid who applies to schools that he has no intention of attending. Not planning to attend is likely to come across in other non-stat portions of the application as well, which are usually important for admission to highly selective colleges.
In any case, while there may be a small portion of high stat students who apply to colleges that they have no intention of attending, a hard limit does not target only this one small group. Instead it impacts many other groups of students who have legitimate reasons for applying to larger number of colleges and would be negatively impacted by such a restriction.