The process of Halacha is complex. Once a Torah law is transmitted to a Mishna by the Tannaim, it gets further discussed in the Gemara by the Amoraim.
The goal of this process, is to put the law into practice for the general public. It is often necessary to standardize matters, for the purpose of simplicity.
One such example comes from בבא בתרא in the situation of establishing possession of a field. The Rabbis needed to devise a system of protection for the purchaser as well as the seller. They were also concerned that a squatter might illegally take someone’s property. They instituted a three year transitional period where the purchaser was expected to hold on to his document verifying the sale, and the original owner was also given this time to protest against the squatters.
When a suggestion was made as an alternate method of חזקה, possession, it was rejected with the words, אם כן נתת דבריך לשיעורין, if so, you have caused a situation of subjectivity.
The more one delves into the Halachic system, the more one appreciates the wisdom and sensitivity of the Rabbis.