Why does setting my column as Always Encrypted change its collation from SQL_Latin1_General_CP1_CI_AS to Latin1_General_BIN2?
SQL Server 2017 documentation:
Always Encrypted is not supported for the columns with the below characteristics:
(...)
String (varchar, char, etc.) columns with non-bin2 collations
(...)

Source: Always Encrypted

Looks like it is changing in SQL Server 2019:

Since its initial release, Always Encrypted has had a restriction regarding the use of collations: non-BIN2 collations are not allowed for character string columns encrypted using deterministic encryption. This restriction also applies to enclave-enabled string columns.

The use of non-BIN2 collations is permitted for character string columns encrypted with randomized encryption and enclave-enabled column encryption keys. However, the only new functionality that is enabled for such columns is in-place encryption. To enable rich computations (pattern matching, comparison operations), you must ensure the column uses a BIN2 collation.

Configure Always Encrypted with secure enclaves