France: 70 million people. 348 Senators. 5 year mandate. Each French Senator represents a small region of France. Banned from having any second job.
Britain: 70 million people. 831 Lords and Barons. Overwhelming from Southern England. No second-job ban. Several are paid lobbyists. Lifetime job security. Many in their 70s and 80s get paid to show up, have tea and play cards with friends.
Because French senators are paid per month, while Lords are not salaried, instead claiming per day they sit in the house. The idea is to have accomplished people in their field come and sit in the Lords on days when their expertise would be useful, rather than to have a professionalised body where members are expected to sit every day of the parliamentary session.
So an eminent technologist may be made a Lord, and would be useful when such matters are discussed, but perhaps not so useful when debating agricultural land use.
This is one of the reasons why there are so many members. They aren’t all expected to gather at the same time in the same place.