A number of years ago I met Rabbi Nota Schiller Shlita, Rosh Yeshivas Ohr Someach Yerushalayim. He told
me this beautiful Vort of his. I apologize for inaccuracies and not being eloquent as the Rosh Yeshiva is.
We find non committed Yidden have little or no connection to the Yom Tov of Shavuos, compared to other Yomim Tovim.
The reason for this is. all other Yomim Tovim have a Cheftza Shel Mitzva (Shofar,Lulav,Matza,Menora Megilla etc.)
The Yom Tov of Shavuos- Zman Matan Toraseinu has no Cheftza Shel Mitzva.
Torah has no boundaries and no limitations. It is infinite..
Objects on the other hand are finite. They come in sizes,weights boundaries and are limited.
When celebrating the infinite Torah, we can't do it with a Cheftza , which is finite and has boundaries.
In place of having a Cheftza Shel Mitzvah we stay awake all night to learn.We learn without limitations night & day.
This is what Shlomo Hamelech meant (Drush) when he said in Shir Hashirim (2:7) :
אם תעירו ואם תעוררו את האהבה עד שתחפץ
Staying awake Shavuos night and learning Torah turns it into חפצה של מצוה .without boundaries