Why ADO.NET instead of entity framework

These are nested block. Entity Framework is build on top of ADO.NET.
ADO.NET handles raw Sql connection and Sql query between your app and a database.

Entity Framework is a much higher level framework. Internally it creates and run query with ADO.NET, but it present an object model of the database and support LINQ (C#) query.

while it is much nicer to use and less error prone it suffer from a few shortfalls. mostly performance. Not really because EF has bad performance, but because:

1. it is extremely easy to write very inefficient SQL query using C#. And it is a common issue with junior developers. BTW this is easy to fix with a bit of investigation with LinqPad, for each query.
2. it very easy to inadvertently write a few lines which unexpectedly make a lot of database query. Easy to fix with proper DatabaseContext configuration (I personally think the default configuration of DB context is a source of endless such problem)

I suspect your senior want to use ADO.NET for either of 2 reason;
- they don't understand Entity Framework and they are worry because they heard of performance issues
- they know both well, but they are worry about their team ability to work with EF well