Why do I need form 8606 T when I have 1099 R

Form 1099-R reports your distribution (income) and Form 8606 tracks the basis in IRAs that have nondeductible (nontaxable) contributions as part or all of the balance of the account, to keep track of taxable and nontaxable amounts.

You report distributions from those types of account on Form 8606 to update the basis year-to-year and you also report contributions on the form to update the basis as well.  For more information see: What is Form 8606?

Form 8606 is also required to report any Roth conversion from a traditional IRA even if you do not have basis in nondeductible traditional IRA contributions.