We were relatively near to the Metro at our hotel in Lisbon (Marriott Moxy close to Picoas station), but we wanted to do a bunch of stuff in the AM before our afternoon flight, so we ended up collecting our luggage and calling an Uber just to be safe & quick rather than making going by mass transit (our normal option). Uber - hotel to airport - was just 7 Euros (without tip). 2 passengers with our luggage. Mass transit is cheap and effective, by it is hard not to justify the 7 Euros trip which saved us a heap of time and we got a pleasant chat to the airport. No cash or CC needed - just the app.
In general, I find using the mass transit option to be a good idea and a good "deal", but it does pay to consider all options at our disposal so time, cost, and convenience can be weighed.
A good idea for almost any airport, Lisbon included, is to visit the airport's website ahead of time and click on their "transportation" options (Lisbon's site it is: "Access & Parking"). Knowing where you can pick up the train/taxi/shuttle/uber after you land and maybe play through the options available is pretty useful.