You're probably referring to ALPA's guidance that items such as "transportation between places of lodging or business and places where meals are taken, telephone calls, laundry, cleaning and pressing, the mailing costs of filing travel vouchers, and payments for employer-sponsored credit card billings" are not considered incidental expenses. You are misinterpreting the transport line item because you are not paying the fare/fee for the transportation itself, which is a item separately reimbursed had you paid.

The tip portion is addressed separately, and specifically, under the definition of an incidental expense. Examples:

From IRS Publication 463: "The term "incidental expenses" means fees and tips given to porters, baggage carriers, hotel staff, and staff on ships."

GSA on per diem:
"What is considered an incidental expense? The Federal Travel Regulation Chapter 300, Part 300-3, under Per Diem Allowance, describes incidental expenses as: [F}ees and tips given to porters, baggage carriers, hotel staff, and staff on ships."