1) There would be a greater severity if done in a sacred place rather than at home.
2) There is a difference of doing a sin in private then going out in public and sinning openly. The latter is corrupting society which is another sin in itself. If a person drank alcohol at home privately this is a great sin but imagine someone drinking alcohol while at the Holy Kaaba for example. This would be of a greater magnitude.
We have similar in regards to good deeds. If someone prays at home it is good but isn’t it better to pray in vicinity of the Holy Kaaba or one of the shrines of Ahl ul Bayt (as)?
3) No one should make excuses to justify their committing sins