Lenihan, who was in charge of Graham Henry's Lions on their 2001 tour of Australia, has questioned why crowd figures for Magners League fixtures in Wales are falling considerably short of the 10,000 mark.
The 50-year-old ex-Munster second row has been impressed with how rugby is prospering in his native Ireland and he admits he expected the success of the Lions tour to have a similar impact in Wales.
"The infrastructure (in Wales) is superb. They have lovely new stadiums at the Scarlets and Blues but, like the Ospreys, there were thousands of empty seats," Lenihan told the Western Telegraph.
"The Scarlets have only moved two or three miles along the road, but they only attracted just over 6,000 for Magners title holders Munster. Why?
"There was only 7,000 at the Ospreys against European champions Leinster.
"I find those figures amazing because I thought, after the Lions tour, Welsh rugby would be buoyant with people wanting to go and watch matches.
"You would think there was a lot to build on, but it doesn't seem to have happened so far.
"Rugby over here in Ireland is buzzing. Munster had sell-out crowds of 10,000 in Cork for both their pre-season friendlies, against Sale Sharks and London Irish. So to see the situation in Wales is a little bit worrying."
And while Lenihan believes the absence of a number of frontline Lions may be affecting the numbers of supporters that turn out in Wales, he sees the continued rest of some of the Irish Lions as a good thing for Irish rugby as a whole.
With 2009 Lions skipper Paul O'Connell and co still completing their recovery from a long, hard season last time out, Lenihan feels the strength and depth in the squads at Munster and Leinster can only be getting better from the experience and game time being gained by their fringe players.
"When people like Ronan O'Gara, Paul O'Connell, David Wallace, Brian O'Driscoll, Rob Kearney and Jamie Heaslip are missing, the guys who come in see it as a chance to fight for a place," added Lenihan, who toured twice with the Lions as a player in the 1980s.
"That puts more pressure on the Irish guys, when they come back, to perform.
"If you win tight games away, like Leinster and Munster did at the weekend, it improves the mindset of the players."