In the European languages, including English, there are words which either appear exclusively in the plural form or do so with particular meanings. Thus, for instance, the Russian word часы ‘clock/watch’ is a plurale tantum in the meaning of a timepiece, the singular form being used to mean ‘hour’.
In English there is a long history of pluralia tantum such as qualifications, finals, negotiations, etc., but in contemporary speech (especially American, but not only) these words are being misconstrued to mean things rather than activities (the latter being their proper semantic category). Thus the last match in a tennis tournament is properly called “(the) finals,” NOT “the final,” but this normative and traditional form is now routinely being replaced by the word in the singular. Speakers who make this mistake evidently take the event to be a thing rather than an activity, whence the change in morphology.