The First and Second Books of Maccabees, being included in the LXX, shows that they were indeed considered religiously important to Jews from antiquity.
As to why they are not in the Jewish “Bible,” one must not impose the Christian view of canon with how Jews have built up the Tanakh. Traditionally the Tanakh is a collection of works written in the Hebrew script. The idea of “canon” is actually a Catholic one, and the guidelines used by Christians (i.e., only those books within the canon are considered inspired and thus the only books which are the written Word of God) are not necessarily applicable in the same manner in regards to how the Jews consider the Scriptures.
The long-passed stories of a “Council of Jamnia” which stated that Jews developed a “canon” in 90 CE in response to the growing Christian movement is no longer accepted as an historical event by scholars (it was a hypothesis developed by Heinrich Graetz that many Christians and others mistook as an actual event until recently). The Tanakh as Jews have today was shaped by factors not limited to those of the Jamnia hypothesis or used in developing the Christian Bible.
That being the case, the fact that these books do not appear in the Tanakh (Jewish collection of “Old Testament” books) doesn’t mean that these writings are not important, lack authority, or cannot be viewed as authoritative. For Jews the Word of God extends beyond the Tanakh.
The irony may be how we Christians often mistakenly judge Judaism and the Jews by standards which we use but do not apply or exist in Jewish thought. The fact that writings are not part of the Tanakh does not mean that authentic history has been left out of the Jewish collection of religious books or that the Jews believe that God does not speak through other writings which are not part of the Tanakh. A book need not be of the Torah, the rest of the Tanakh, the Talmud, etc for Jews to consider them important or holy or of God. Jews generally do not consider “inspiration” as a rule for inclusion or even a facet of the Holy Scriptures in the way Christians understand and use the term.
Be assured that Maccabees is often referred to and used by Jews not only in reference to Chanukah but at other times.