I think both things can be true. If you apply for a job where the application requires salary history, having a higher past salary can show a potential employer that you had $X worth of responsibilities at your last job. Not saying it' a great metric but it's there.

Many job applications request you to list your current salary, so if you don't you run the risk of submitting an incomplete application. It is what it is. Maybe they'll lowball you if they see you haven't made much at the current job, who knows. Biggest thing on salary expectations is to bet on yourself and shoot high. They will never offer you more than you quote them unless they're somehow obligated to. Worst they can do is laugh at you and not offer you the job. More likely they'll laugh at you and offer you something lower than you quoted but possibly still acceptable to you. I learned this the hard way when a less experienced candidate made more than I did because they requested an outrageous starting salary for the industry.