The tshirts, if they end up abroad, contribute to ruining the local textile industry.
Many developing countries had local industry producing fabric and clothes, but they really struggle to compete with free or almost free waste Western clothes.
When you say "local textile industry" are you thinking of cotton growing, yarn spinning, fabric weaving, or shirt cutting/sewing? Because those are all totally different things done in totally different parts of the world. There is no longer such thing as "local textile industry". A single strand of cotton is better traveled than most of us.
Last time I was in an African country there were people wearing shirts like "Atlanta Winners 2019" when it was some other baseball team that won in 2019. So similar to what you describe.
Those shirts were probably made in Asia, but ruin the African clothing industry.
Many developing countries had local industry producing fabric and clothes, but they really struggle to compete with free or almost free waste Western clothes.