First you have a new roof and new gutters. Then over time, the small granules on the asphalt roofing shingles start to wear and come loose. During time of wind and rain, the loose granules end up collecting in the gutter.
Birds and wind contribute to seeds and other plant materials growing in the gutter. Soon you have a gutter garden. Maybe if you grow herbs, it may help. The gutter is filled with debris and water does not drain properly. The gutter starts crowded and leaks. But at least your gutter garden herbs are doing fine.
Word of advice – inspect your gutters every quarter and make sure it is free of debris and in good condition.