not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near (Heb 10:25).
This is a popular prooftext for mandatory church attendance. That's because the NT says so little explicitly on the subject of church attendance.
However, the motivation behind this verse is more specific. In the broader context of Hebrews, Christians are facing the threat of persecution and discrimination. Disassociating themselves from fellow Christians, and the public life of the church, is tempting. That limits their exposure.
Nowadays we see the equivalent on the part of "progressive Christians" who go out of their way to distance themselves from Biblical norms for gender and sexuality, and publicly disown Christians who remain faithful to Biblical revelation. They are motivated by fear. They do so to cover their own flank.
While that's understandable from a psychological standpoint, it's not coincidental that this verse is the lead-in to a dramatic passage on apostasy, and its dire consequences.
Under threat of persecution and discrimination, some professing Christians will openly disavow the faith. But for others, the first step is to redefine the faith and separate themselves from Bible-believing Christians and Bible-believing churches.
Hebrews treats both protective strategies as apostasy. You can deny the faith by your actions as well as your words.
The same dynamic is present here:
Brother will deliver brother over to death, and the father his child, and children will rise against parents and have them put to death (Mt 10:21).
Denouncing a Christian to the authorities curries favor with the authorities. To betray a Christian makes you a loyal subject of the state. Choose your treason.
As I say, we see this happening in America.