I am herewith attached the abstract of a paper entitled "Why are Plant Names Changing so Much? by Alan S Weakley.
I think this will solve your doubts.
The scientific names of planes continue to change, seemingly at a faster rate than ever, which challenges the broad and diverse group of users of those names. Why do names change? Some changes are nomenclatural. while the majority result from new research and judgments about the taxonomy of plants. A variety of factors contribute to the level of changes. Traditional plant taxonomists continue to discover plants and reclassify those already known. New molecular phylogenetic techniques provide new data that clarifies taxonomy, especially at the level of the genus and above, resulting in changes in the circumscription of genera. A more worldwide community of plant taxonomy has emerged, fostered by the Internet, and taxonomic studies have broader geographic perspectives, resulting in changed opinions about relationships and more rapid communication of those changes. In the art of plant taxonomy, the “splitters” have largely regained influence, after a period of several decades in which “lumpers” were generally in the ascendancy, at least in North America. The result is a large number of name changes in plants, challenging many users, particularly those who are not professional taxonomists—land managers, ecologists, gardeners, and conservationists. A greater effort by authors of floras and other products designed for use by the broad botanical community should make the effort to communicate the changes and reasons behind them.