When starting seeds in small containers or flats, be semi-frugal with them for the following reasons:
In the case of tomatoes, peppers and others, only one sprout can be allowed to develop within a several square inch area. If your seeds are new with a high germination rate, more than two seeds in that area could be judged exceeding semi-frugality.
Avoid the angst when having to pull out and discard those sprouts.
Seeds cost money. If you don’t have other gardener friends to share with during the current season, most seeds will still be viable for some years past the year for which they were packed, albeit with lower germination rates. Protect seeds by preventing contact with moisture or allowing critters access to the seed box.